Spots and yellowing on top leaves

Simpex

New Member
Hello fellow growers!

This is my first attempt at growing anything indoor and so far it has gone pretty well. But now I'm starting to have some really bad issues with one of my 4 plants, a Blue dream, even though it's otherwise significantly outperforming the other 3, a white widow and 2 northern lights. BD is a couple of inches taller than the rest. I'm in my 8th week of flower. Let me try to sum up what I've been doing so far.

The setup:

- growing in a 80x80x180cm (2,5 x 2,5 x 6ft) tent in a 30m2 (300+ ft2) room where fresh air is being pulled in only approx 14 hours per day, sadly I have no control over this, I open the windows when possible during the day,

- coco coir with 25% perlite in 10l (2.5gal) smart pots,

- a 200m3/h (120cfm) fan with two scrubbers (I tested multiple ones and having only the one inside the tent doesn't remove the odor, so I had to add another one on the outside - at which point there's no smell whatsoever). I know the air should be pulled out of the room entirely, but right now I don't have that option. A passive intake at the bottom of the tent, about twice the size of the exhaust,

- two Viparspectra 450 LED lights (400W at the wall), I have them at about 40cm (17in) from the tops of the plants, oscillating fan right at the top buds,

- 22C (72F) and 42% humidity slightly below the scrog net.

I've been using GH Flora trio, starting lower but then mixing their recommended strength. One mistake I've probably made was not giving enough plain, pH-ed water between the feedings, I now feed only every other watering, for about the last 5 weeks or so. Adding Cal-mag too, but I started adding it only after about a month into veg. I flushed 4 times through the entire grow, not really flushing but watering with twice the usual amount and getting 1/2 of that out. I see no salt build up on the Blue dream's coir. I always remove the excess to the best of my ability, the pots aren't sitting in a puddle. pH in veg was 5.6-6.0, I now water with 6.1-6.3, the drain was tested yesterday and it was exactly the same as the water that came in, at 6.2. Tap water isn’t too hard, pH 7.

Now, I know this is a problem prone setup, but does anyone have a clue what I could do to try and remedy the situation with the spots and leaf burning? The lower part of the plant isn't showing any major problems, a couple of leaves fall off by themselves every now and then, but it's late in flower. Could it be bud rot? Nutrient lockout? LEDs too close? Not enough fresh air? The thing is, the buds are pretty big, but don't seem to be very frosty. Widow an northern lights have healthy looking buds. I guess, this being week 8 of flower, I can't expect miracles, but still, any ideas as to what I should do to try and squeeze some extra trichomes from that? :)

Thank you so much for your help!
 

Attachments

Last edited:

polishpollack

Well-Known Member
Ferting every other time might be too much, even in coco as it will trap nutrients. Your leaves look like the plants are being over ferted. I'd stop the fert and just give water for a while when dry. Coco probably holds quite a bit of water, but I don't know from experience as I've never used it. In pics, it tends to look like it swells up when wet.
 

Simpex

New Member
Thanks! I've been adding slightly less nutes the last few weeks.

I'm going to remove the scrog today so I can move her and do a proper and thorough flush. When that's done, should I wait for the coco to dry and then add 1/2 nute strength?
 

shawnery

Well-Known Member
I don't do coco, just harvested a little 1 eighth plant in it, but I've read many times that you never feed just water. Obviously most of your plants are doing fine but.

My understanding is that you feed till you have about 20% runoff each time. If you read your ppms going in and read them out you will know how to stear the nutrient mix.

Instead of feeding only water that often you should be testing your runoff from your 20% runoff and lower your ppms to lower your runoff or raise your ppms to raise your runoff.

Take it with a grain of salt but that's my understanding and experience in my small 1 plant grow. I'm sure some more knowledge grower will knock me down though.

Either way I suggest always searching on the net for the answers to what ever solutions you find on here and don't restain yourself to only cannabis growing.
 

Simpex

New Member
Yes, when I just water, I always add some Cal-mag, that's what the local store guy tells me. I don't have a ppm meter, I guess that should be on my priority list for the next grow. And only growing one plant in that small tent with proper drainage.

I feel like I've searched the entire internet and it seemed to me like the beginning of manganese deficiency (last photo) but considering my setup I guess that shouldn't be the case.

So, for now I guess a thorough flush and then ease on the nutes. I'll post the results if it gets any better.
 

jondamon

Well-Known Member
Imo this is a classic case of Ca deficiency.

However though.

The trouble with calmag products is that you have to add both together.

And too much of one can cause symptoms of a deficiency of the other. Too much Mg looks like Ca def.

Too much Ca can look like Mg deficiency.

Personally I prefer a separate Ca (I use canna mono Ca) for calcium during flowering.

I don’t add any extra Ca during veg.

However every 2 weeks though I sprinkle a pinch of Epsom salts on top of my soil and allow it to be watered in when I water during both veg and flower.

Then during flower I keep up with the sprinkle every other week and on the alternate weeks I add 1ml per litre of canna mono Ca to my feed.

Not much you can do now to be honest.

You could try some finishing nutrients such as GHE RIPEN to try and help and Trich formation but IME they don’t work all that well.

You’re better off just letting them finish properly and cut them when they are actually ready rather than when breeders tell you they should be ready.
 

Simpex

New Member
I believe it really might be a Ca or Mg problem. Thing is, I just noticed that the CaMg bottle(Aptus CaMg Boost) says add once weekly at 2.5mL/5L of water and I've been adding it pretty much every watering (every two days atm) as the store guy suggested(coco apparently needs lots of Ca)... crap! The CaMg booster has a 9:9:2 ratio of N:Ca:Mg! Could the nitrogen be a problem as well? And the bottle says never mix with other stimulators with extra phosphorus. Flora trio isn't a stimulator, right? I've been adding the CaMg with it as well, always CaMg first, though.

jondamon, do you think some epsom salts would benefit me in this stage, since the ratio in the booster is clearly toward the Ca.
 

jondamon

Well-Known Member
Personally I always recommend when growing In coco that people use a nutrient line with Ca around 3-5 in comparison to Mg at around 2.

With an NPK of around 5-3-4

Right now being so late in flowering I wouldn’t worry about what you can add or do to fix at this late stage.

You have at most 2 weeks left.

Next time check what Ca is in your GHFLORA series if it’s around 5 and Mg is around the 2 mark then you’ll only really need some Mg to get a healthy grow all the way through flowering.

I personally utilise Ca during flowering to help with extra uptake of ions during heavy feeding times.
 

Simpex

New Member
Great, I’ll keep that Ca to Mg ratio in mind for the next grow.

As for the lights, I thought of that too and managed to pull them up a bit so they’re at about 45cm, can’t move them higher.

After flushing the pants eventually need to be fed, I guess? Usualy after I flushed I just let the coco dry (2-3 days) and then fed. That’s ok, right?
 

shawnery

Well-Known Member
No! That is not all right, I think!

You should never let it go completely dry and especially after flushing.

That just sounds like a recipe for disaster?
 

jondamon

Well-Known Member
Personally I don’t give my coco plain water.

If I’m concerned with a possible salt build up I use 50% of the current strength feed.

For example now I’m currently feeding at 1.4EC.

if I suspected a salt build up I would water with half of that EC For 2 or 3 feeds at 0.7EC.

Then continue back on track with the 1.4EC next week.

This is my plant at 5 weeks and I’ve just flipped to 12/12.

I’ve trained sightly with topping and super cropping and stripped aka lollypopped my lower growth pre stretch.

I use the DUTCH PRO line of nutrients and straight coco no amendments.

I’m a personal grower so I fluctuate between 1 and 4 plants growing depending upon how much harvest I have left when I start the next one. I also like downtime between grows.
 

Attachments

jondamon

Well-Known Member
No! That is not all right, I think!

You should never let it go completely dry and especially after flushing.

That just sounds like a recipe for disaster?
And very true.

At this stage I feed my plants every other day.

Coco needs to have high moisture content as it retains a high oxygen to moisture ratio better when saturated and allowed to drain 20% runoff.
 

jondamon

Well-Known Member
jondamon, that doesn't make sense right now. how does coco hold more oxygen when it's saturated with water?
Peopleworry about over watering with coco and unless your rootzone is submerged or in a puddle etc it just can’t happen due to the way the oxygen is pulled back into the substrate after watering sufficiently to gain approx 20% runoff.
 
Top