Cannabis seedlings look like they are dying

Hi there, first time poster and first time grower here.

I apologize in advanced for my lack of experience, for any mistakes i may have made in the grow or the post and potential ignorance in the matter, but I've recently run into a bit of a pickle.

I recently bought a budget indoor growing setup to grow medicinal cannabis for my mother who is a cancer patient and myself who has anxiety disorders. My setup includes a 70cm x 70cm (2.3ft x 2.3ft) Mars Hydro tent, a TS-1000 Mars Hydro LED Grow light and a 100mm metal inline extractor fan (no carbon filter as of yet) after getting things set up i germinated (non feminized) 5 seeds (that i received as a gift) to begin my journey.

One of the five seeds were cracked and didn't sprout a tail so i germinated a 5th a day later. Having all 5 planted into cups with my soil mix, the first seedling sprouted and by 2 days later all 5 had sprouted, they are planted in a soil mix composed of 5 gallon washed Coco peat, 5 gallon compost, 3 gallon worm castings and 2 gallon perlite, as well as the addition of 2 cups 5:1:5 rose and flower mix, 1.5 cups trace minerals, and 1 cup bone meal all thoroughly combined(this is a recipe provided by a popular YouTuber Cali Green, who was the major inspiration for me growing medicinal cannabis indoors).

All seemed to be going good as seen in the first photo marked "before" (26 April) things were looking great, healthy green leaves, watering every second day with Reverse osmosis water, no sign of pests. 10 days into the process i watered with a mixture of "beneficial bacteria" 1ml/L, "Seaweed extract" 5ml/L and half a teaspoon of molasses dissolved into the Reverse osmosis water, i also aerated the water with an air pump as well as put a quarter cup of worm castings and a quarter cup of compost into a strainer bag and let the "compost tea" brew overnight (another recipe from Cali Green's YouTube channel)

After watering the plants with this mixture, a couple of days later i noticed that the tallest seedling's true leaves started turning yellow , i was concerned that the seedling was receiving too much light so i put it in the very edge of the tent where the light was less intense, i also connected the extractor fan (on slow speed) and opened some more ventilation in the tent as the LED grow light had a tendency to raise the temperature in the tent by a good 5-8 degrees C when it was on, i also raised it to as high as it could go from the original approx 28 inches from the seedlings. As the days went on however the seedling wasn't getting anymore color in its leaves and the baby leaves had also started to wither and die (as seen in the photo marked "after" 3 May), but then i noticed that all the seedlings had also all stopped stretching after i watered with the "compost tea".

I have attached files of all the seedlings marked 1-5 and all are strangely in very different states. (1.) is the seedling that first popped out, stretched wildly and stopped stretching and leaves died after being watered with compost tea, it however is starting to grow a tiny set of new true leaves that are getting bigger each day, and the stem is still strong so ive got hope. (2.) is the seedling that i accidentally knocked over before they had even sprouted (in an effort to save the seed i scooped it all back into the cup) and as a result it is now growing out the side, but has stopped stretching since watering with compost tea, strangely this is the healthiest looking one. (3.) was the seedling that i germinated a day after the first four so i was expecting slight delays in the growth compared to the others, but it too has stopped stretching since the watering with compost tea. (4.) and (5.) are in a very similar situation, also having stopped stretching since watering with compost tea, but now also (i'm not sure if its visible in the photos) the tips of the true leaves are drying up on both of the.

The large pot with the bigger seedling is an feminized auto flowering variety I randomly planted (in the same soil mix) that is doing OK (but could be doing better). I am not entirely sure as to what i should do now as i haven't seen any noticeable growth. Its recently gotten very dry where i live in order to maintain good humility I've added a couple of lids to the cups in an effort to try save them. The LED has an adjustable driver so i am able to reduce the light intensity, but i haven't messed with that yet as i was worried about damaging it, so i just raised the height to as high as it could go.

Any advice/criticism would be appreciated as well as tips to maybe revive these poor looking girls. If more photos are needed i will take some.

Thanks

Seems like a lot of nutrients in soil and then you dump a tea with nutrients on top? I’m not familiar with his method but maybe you’re over watering it?

the first one looks toasted with nutrients

Wattzzup said:

Seems like a lot of nutrients in soil and then you dump a tea with nutrients on top? I’m not familiar with his method but maybe you’re over watering it?

the first one looks toasted with nutrients

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Thank you for speedy response. They are at such a fragile stage i don't want to over stress them anymore than they are. What would you suggest i do in the case of a nutrient burn?

I would suggest to wait for a few responses from more knowledgeable people. I don’t want to freak you out or send you down the wrong path.

May I suggest you don't use the cup lids to create a humidity dome.

Cannabis seedlings do better in a low humidity climate, you run the risk of rotting them by overwatering and high humidity. It also looks like your growing media holds a lot of water, so also watch out for dampening off

https://en.m.wikipedia.org/wiki/Damping_off

It can also become a issue if you keep your young seedlings too wet and humid.
Cannabis is very tolerant to low humidity, less so to high humidity.

Also you should try to never wet the leaves, especially under artificial lights, as it burns the leaf, this maybe what happened in your case from watering or humidity droplets

If you get water on the seedling use a absorbnt paper towel to soak up the droplet, if larger plants get water on them , try to keep a fan on them so they dry out fast, or shake the excess water off gently, or as best practice water just before lights out. The water droplets act kinda like a magnifying glass under the artificial lights and burn the leaf.

RangiSTaxi said:

May I suggest you don't use the cup lids to create a humidity dome.

Cannabis seedlings do better in a low humidity climate, at a guess I think you rotted them by overwatering and high humidity. It also looks like your growing media holds a lot of water, dampening off https://en.m.wikipedia.org/wiki/Damping_off

Can also become a issue if you keep your young seedlings too wet and humid.

Also you should try to never wet the leaves, especially under artificial lights, as it burns the leaf, this maybe what happened in your case from watering or humidity droplets

If you get water on the seedling use a absorbnt paper towel to soak up the droplet, if larger plants get water on them , try to keep a fan on them so they dry out fast, or shake the excess water off gently, or as best practice water just before lights out. The water droplets act kinda like a magnifying glass under the artificial lights and burn the leaf.

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I never considered that, i was under the impression that it was helping. I will start watering at the bases of the plants to ensure the stems and leaves stay dry during this stage.

You also mentioned "damping-off" upon looking into it said that homemade recipes including garlic can be used to cure the seedlings, i will look into that and see if applying this to one or two of them "Garlic spray" will help.
"https://underwoodgardens.com/damping-off-causes-and-control/"
"https://en.m.wikipedia.org/wiki/Damping_off"

Gavin_B said:

I never considered that, i was under the impression that it was helping. I will start watering at the bases of the plants to ensure the stems and leaves stay dry during this stage.

You also mentioned "damping-off" upon looking into it said that homemade recipes including garlic can be used to cure the seedlings, i will look into that and see if applying this "Garlic spray" will help.
"https://underwoodgardens.com/damping-off-causes-and-control/"
"https://en.m.wikipedia.org/wiki/Damping_off"

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I don't think you have dampening off, but your climate is right for it.

The best thing you can do is remove the lids and stop watering or misting until they dry out. Your kindness may infact be what is killing them.

Damping off is fatal, there is no cure, you can prevent it my keeping your plants warm, your media moist-dryish but never wet and your humidity low.

most info online says keep seedling humidity high. That’s what I’ve been doing. You’re saying it’s not needed?

Wattzzup said:

most info online says keep seedling humidity high. That’s what I’ve been doing. You’re saying it’s not needed?

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Yes I'm saying high humidity is more of a issue in most cases, and the growing media needs to be moist but should never stay wet.

RangiSTaxi said:

Yes I'm saying high humidity is more of a issue in most cases, and the growing media needs to be moist but should never stay wet.

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So the high humidity plus over watering is deadly. Is that what you’re saying? I just want to make sure I’m not slowing my seedlings down with a bottle

RangiSTaxi said:

Yes I'm saying high humidity is more of a issue in most cases, and the growing media needs to be moist but should never stay wet.

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Would increasing the size of the drainage holes in my cups help? they arent huge, but could be bigger.

Disregard I get it now. You’re saying that high humidity is not even needed and more often a problem. Damn I’m high. Every time I read it, it seemed different.

Wattzzup said:

So the high humidity plus over watering is deadly. Is that what you’re saying? I just want to make sure I’m not slowing my seedlings down with a bottle

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Yes correct, if your humidity is too high over a too longer period you risk losing your freshly germinated seedlings to fungal disease. There is a balance but your growing media needs to slightly dry out between misting and watering to prevent the environment where fungal diseases can arise.

Gavin_B said:

Would increasing the size of the drainage holes in my cups help? they arent huge, but could be bigger.

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There's probably no need but it won't hurt, just mist/water less often.

Also when germinating seedlings it's always best to use store brought seedraising mix, it's very free draining, light and fluffy and doesn't hold too much water, and has a good air to water ratio., often seedraising mixes include a slow release fungicide in the seedraising mix.

RangiSTaxi said:

Also when germinating seedlings it's always best to use store brought seedraising mix, it's very free draining, light and fluffy and doesn't hold too much water, and has a good air to water ratio., often seedraising mixes include a slow release fungicide in the seedraising mix.

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I am trying to look at growing organically if at all possible, so im not sure if the pesticides would affect that and i live in a very remote part of the country so its hard to get my hands on specialized mediums, hence why i tried to do my own mix. i think in future i will add more perlite and coco to the mix for the seedling stage to get that added oxygen and draining

Thank you both for all the help, I will take the lids off, wait till the cups weigh less and the soil dries out, then spraying only on the base when dry.

I will be sure to post updates in the next 2-3 days or so.

What he’s saying is just a plain, good draining soil with min to no nutrients meant for seedlings. Most rural area stores have seed starting mix.

Yes if you make your own potting mix or seedraising mix you will want 20 -35 percent pumice sand, or if you cant source pumice sand, then you can use perlite, or washed river sand as a replacement. Most seedraising mixes don't contain fungicide, but they all are cooked/heat treated so they are fungi spore free as well as weed seed free. The pumice sand size you use is relative to the plant size your growing, for seedlings you will want a small grain size so as the seed can easily germinate i.e push though the soil and grow roots quickly. The pumice sand keeps the air to water ratio high, prevents fertilizer build up, and keeps the growing media free draining and light, making it easier for the roots to grow through. If you can't get seedraising mix, you can sieve regular potting mix to a smaller particle size , so you just have the finings for the seedlings and no big chunks.

Seedraising mix recipe
1 part vermiculite,
1 part coir (coconut fibre)
1 part pumice sand/perlite
1 part compost


Sieve each ingredient to a fine size.
(But not the vermiculite)

(If you don't have vermiculite use 2 parts sieved compost instead of just 1)

Then mix well and sieve again.

Then add the vermiculite , mix again.

Add

a sprinkle of blood and bone, sieved dry worm castings and kelp/seaweed powder to provide some nutrients mix well. If non organic, add seedraising slow release osmocote or similar and mix.

Water and then mix once more and then your ready to use.

Although I would still recommend the store purchased seedraising mixes over the home made.

The potting mixture used in the 1st original post in this thread should be fine once the plant is established and at least 15cm tall and the germinated seedling has a semi-root bound seedling pot and ready for up potting. It's more suited to a flowering stage potting mix rather than a seed germination mix as it contains a lot of nutrients more suited to a larger plant.

In saying that every thing should go fine from now on if you reduce time between waterings , keep the leaves dry and remove the humidity domes.

P.s you can lower your light to 60cm (24 inches) above the seedlings as long as your leaves stay dry it won't harm or burn them, currently it's far too high. In a week or two you can lower it a bit more again.

RangiSTaxi said:

Yes if you make your own potting mix or seedraising mix you will want 20 -35 percent pumice sand, or if you cant source pumice sand, then you can use perlite, or washed river sand as a replacement. Most seedraising mixes don't contain fungicide, but they all are cooked/heat treated so they are fungi spore free as well as weed seed free. The pumice sand size you use is relative to the plant size your growing, for seedlings you will want a small grain size so as the seed can easily germinate i.e push though the soil and grow roots quickly. The pumice sand keeps the air to water ratio high, prevents fertilizer build up, and keeps the growing media free draining and light, making it easier for the roots to grow through. If you can't get seedraising mix, you can sieve regular potting mix to a smaller particle size , so you just have the finings for the seedlings and no big chunks.

Seedraising mix recipe
1 part vermiculite,
1 part coir (coconut fibre)
1 part pumice sand/perlite
1 part compost


Sieve each ingredient to a fine size.
(But not the vermiculite)

(If you don't have vermiculite use 2 parts sieved compost instead of just 1)

Then mix well and sieve again.

Then add the vermiculite , mix again.

Add

a sprinkle of blood and bone, sieved dry worm castings and kelp/seaweed powder to provide some nutrients mix well. If non organic, add seedraising slow release osmocote or similar and mix.

Water and then mix once more and then your ready to use.

Although I would still recommend the store purchased seedraising mixes over the home made.

The potting mixture used in the 1st original post in this thread should be fine once the plant is established and at least 15cm tall and the germinated seedling has a semi-root bound seedling pot and ready for up potting. It's more suited to a flowering stage potting mix rather than a seed germination mix as it contains a lot of nutrients more suited to a larger plant.

In saying that every thing should go fine from now on if you reduce time between waterings , keep the leaves dry and remove the humidity domes.

P.s you can lower your light to 60cm (24 inches) above the seedlings as long as your leaves stay dry it won't harm or burn them, currently it's far too high. In a week or two you can lower it a bit more again.

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Thanks so much,

I've printed this all out and will try either get seedling mix or make your suggested recipe for next time rounds seedlings. I'm also glad to hear the soil mix i made is still usable (even if it is only for late veg/flower stages) as i have a huge tote full of it

I will also ensure that i dont over water the seedlings and watch to make sure the deadening of the leaves/discoloring slows down, will post updates in about 3-4 days or so with progress.