Brown leaf spots

Hey all,

hoping someone might be able to shed some light on what this plants condition might be..
Thus far, I’ve had some great happenings on my first grow indoor with a grow tent..
I currently have three plants all doing great, and I’m their last two weeks of flower.
There is one plant however that in the last few days started exhibiting the condition shown in the photo.
it’s the only one of the bunch (4) that has these brown spots.. No rusty dusty comes off on my fingers if I rub the spots. It’s only on the older leaves nearing the top of the plant.
Any ideas on what this might be?
Any constructive thoughts at all would be greatly appreciated! Thanks In advance!!

Pretty classic Ca issue. My best guess, looking at the dark green color of the leaves, is that a bit too much N is locking out Calcium. Ease off on N, and keep up the calcium. If you’re not feeding N, up the Ca anyway! The other option is to give it a good flush, reset the soil and go back to feeding and calmag. (Reduced N). This is for soil, it would also be helpful to know what your media is, your nutes, feeding schedule, and ph of nute water.

Phytoplankton said:

Pretty classic Ca issue. My best guess, looking at the dark green color of the leaves, is that a bit too much N is locking out Calcium. Ease off on N, and keep up the calcium. If you’re not feeding N, up the Ca anyway! The other option is to give it a good flush, reset the soil and go back to feeding and calmag. (Reduced N). This is for soil, it would also be helpful to know what your media is, your nutes, feeding schedule, and ph of nute water.

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Heya!
Thank you for the straight forward concise response..
So I’ve been feeding them in soil, with Age Old nutrients Bloom since I flipped them seven weeks ago.
They’re small plants which was by design as I had been given some spooky stories of plants stretching too much and that causing issues..
In hindsight, keeping them so small is what I assume might be part of the problem leading to the issue you exclaimed in your reaponse. Not much plant/not much nutrient utilization..
They’re grown in ocean forest, feeding less than a normal robust larger plant, once a week still.. PH has been consistently 6.3-6.8..
Thank you so much for your response..
Any other tutelage you could provide would be greatly appreciated..
again, much thanks..

Jeffersonlee9 said:

Heya!
Thank you for the straight forward concise response..
So I’ve been feeding them in soil, with Age Old nutrients Bloom since I flipped them seven weeks ago.
They’re small plants which was by design as I had been given some spooky stories of plants stretching too much and that causing issues..
In hindsight, keeping them so small is what I assume might be part of the problem leading to the issue you exclaimed in your reaponse. Not much plant/not much nutrient utilization..
They’re grown in ocean forest, feeding less than a normal robust larger plant, once a week still.. PH has been consistently 6.3-6.8..
Thank you so much for your response..
Any other tutelage you could provide would be greatly appreciated..
again, much thanks..

Click to expand...

Doesn’t look like you’re providing any Ca (normally found as cal-mag), so I’d get some and start adding it. FFOF is a good soil. Happy growing!

Phytoplankton said:

Doesn’t look like you’re providing any Ca (normally found as cal-mag), so I’d get some and start adding it. FFOF is a good soil. Happy growing!

Click to expand...

What a fool.. apologies.
I have been feeding the recommended dose of cal mag.. (fox farm bush doctor)
Just thought it seemed unusual to see this in one plant and not the rest.
(Plant pictured in the bottom left)

Jeffersonlee9 said:

What a fool.. apologies.
I have been feeding the recommended dose of cal mag.. (fox farm bush doctor)
Just thought it seemed unusual to see this in one plant and not the rest.
(Plant pictured in the bottom left)

Click to expand...

Ya know, some plants are just more sensitive than others,, you could try dropping the ph on the calmag water to about 5.8,.

Phytoplankton said:

Pretty classic Ca issue. My best guess, looking at the dark green color of the leaves, is that a bit too much N is locking out Calcium. Ease off on N, and keep up the calcium. If you’re not feeding N, up the Ca anyway! The other option is to give it a good flush, reset the soil and go back to feeding and calmag. (Reduced N). This is for soil, it would also be helpful to know what your media is, your nutes, feeding schedule, and ph of nute water.

Click to expand...

Technically it's manganese toxicity. I never understood how the Cannabis community has missed this, since I started growing in 74 and learning cannabis nutrition was not an optional task, it was the sole route to financial success over the following 2 decades.

Shortly after beginning my growing career I moved to an area with high Mn in the soil and everything went orange. We had the leaves tested and they had toxic levels of Mn, in the hundreds close to 1000ppm on some varietals. Cannabis cannot tolerate the Mn it accumulates. It needs maybe 25ppm. 40 at most. Cannabis is a hyper accumulator of Mn and I've had countess fights with weeds nute lords who insist on using trace mineral profiles for tomato and selling the extra bottle to counteract it:

My consultant at the time told me to use high amounts of dolomite lime to restrict Mn uptake. I added so much limestone that I locked out pk and also hermed the crop. And at that point I decided to become my own consultant. Nutrient balance is the only factor that mattered in our grows. Everything else could be essentially ignored and the product would fetch full price. Ignore nutrient ratios and the quality slips drastically.

That's why weed was really good in the 80's. We figured that shit out on our own and it had to produce the best bud or you became the drought-only supplier sitting around waiting for everyone else to sell out before old friends would reluctantly call you up. Alot of the difference between today's weed and 20th century weed is simply the ratio of excess Mn to Mg and the way this redirects energy in the mevalonate and methyl erythrol phosphate pathways.

Light burn?


Calimag deficiency?

.




pH issue?





Mn is the heavy metal that fucks up Cannabis worst. Worse than cadmium. Worse than lead. Yet, look at this soil recommendation for hemp:



20ppm Mn? What the hell??? The 0.8ppm already would kill a Cannabis crop in that soil.. Summon Calimag.. Calimag!! Cali Mag Shakti de!



Just thought I'd clarify why pot growers think lower leaf spots could be a immobile nutrient issue. Since the actual purpose of Calmag has kinda been lost on the scene: It's a bandaid for garbage quality relabeled high Mn low carbon high nitrogen tomato nutes.

Very strange, my water has so much Mn in it, it actually makes your hair brittle, never had any issues with it, growing indoors or outdoors..