Help with leaf spot diagnosis

Could this be a fungus? Could this be a pH problem?

This is a Donny Burger veg plant about 3 weeks old in Foxfarm Ocean Forest soil. Only supplements added so far are Foxfarms Grow and Vitamin B-1 both in mild doses. The light source is a 1000W LED. The temp and humidity have been steady at 65-70 degrees and 50-60%. There are six different plants in this space all different strains. All of which looked fantastic until two days ago. Suddenly today only the Donny Burger plant came down with these spots.

Welcome to the forum!

Your girls have been given too many nutrients. Those dark green, waxy leaves show nitrogen toxicity. You shouldn’t have to add supplements for weeks yet in the soil that you are using, which is already hot.

I would flush them to get your PPMs down. Do you have pH and PPM meters? The spots could be due to a nutrient lockout due to pH.


Even with my pH at 8.7 I never got leaves like that. I have GH Florakleen and Sledgehammer on stock now. It kinda also looks like advanced stages if a Cal-mag issue. But I can’t identify those problems as I don’t have to deal with them at all. I’m lucky that way. Sledgehammer FTW. :+1:

And @FlxerPower is correct. Brand new FFOF is really “hot” right out if the gate for about the first 6 weeks.

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Welcome to ILGM, @maxvooo :wave:

ILGM Support Ticket:

What is the strain and type(unknown bag seed, strain name, regular seeds, feminized seeds, auto-flower, etc)?

Indoor or Outdoor? If outdoor, planted in ground or in a container?

Size of space (max height and area, length/width)?

Soil or Hydro? Type of Medium used? System type?

pH? Of the soil or medium (root zone/reservoir/run-off) and of the water and/or nutrient mix that is fed to the plant?

Type and strength of nutrients used? NPK? EC/TDS/PPM levels? Of what you feed it as well as what is in the water by itself and in the soil/medium (run-off), or reservoir.

Temperature? Day vs. night temp or highest and lowest temps? Root zone temps?

Humidity %? Day vs. night

Light system/watts/lumens/FLUX/PAR?

Ventilation system? Size? CFM? CO2? AC, Humidifier, De-humidifier?

Number “weeks/days” from into Season, Vegetative Growth or Bloom/flowering?

Add anything else you feel would help us give you a most informed answer. Feel free to elaborate, but try to be brief and to the point. Short and to the point questions and/or facts will help us help you.

My gut tells me Potassium deficiency. Can you post a pic of the whole plant? The dark green leaves just look wet, to me. Nutrient burn starts at the tips and works its way inward toward the veins. Getting a pH and PPM reading of your runoff is a good idea, but it doesn’t look overfed to me.

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Hmm, that said…why are the leaves wet? And I think I misspoke, I meant Phosphorus. That P/K thing F’s with me. I’m no chemist lol

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Looks like pH issues.
pH in/out and ppm in/out would be usefull.

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I caught the wet leaves but I was looking more at the problem. Yup those leaves are soaked.


It looks to me like they are just very waxy from the nitrogen.

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You can see a few small drops in the second picture. Again, overfeeding would burn the tips first.

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Yep, why are the leaves wet? What are you spraying it with? You’re spraying with the lights on I bet.

I don’t have a PPM meter. I did find that the runoff water from the pot is pH 6.4.

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pH in: 8.4
pH out: 6.4

ILGM Support Ticket Answers:

  1. Donny Burger
  2. Indoor
  3. 5 feet x 7 feet x 8 feet (8 feet is the height)
  4. Soil - Foxfarms Ocean Forest
  5. water pH is 8.4, runoff pH is 6.4
  6. Foxfarms Grow & Vitamin B-1
  7. Temperature 64-72 degrees - taken at plant level
  8. Humidity 45-60% - taken at plant level
  9. 1000W LED 24 hours
  10. 440 CFM 6 inch inline duct fan and carbon filter.
  11. 3 weeks vegetative growth
  12. Additional info - see my brief original post comment
  13. Whole plant picture

Have you tried a slurry test? Just to see exactly where your soil is at pH wise?

8.4in w/ 6.4 out seems odd.

I thought it doesn’t take much to change the pH of the plain water going in. so I wasn’t surprised by the difference. Do you think the values are odd?

It is plain water on the leaves. I was spraying the bottoms of the leaves.

Something is going on. I noticed it on the one photo to the very left.

There is other leaves showing deficiencies. But I’m no expert in identifying them these problems.

pH in the 8s is a little higher going in than typical, could be a sign you need to flush. If you’re putting 8.4 in to get 6.4 out, the soil is probably sitting around 4.5 - 5 or so, starving them of a few things. Also, they look like they could be getting root bound. It’s easy enough to slip the them out of the pot a little to see. Might be time for bigger containers. You may want to use cloth containers or at least drill lots of holes in the containers, on the sides too, for aeration as much as drainage. How are you measuring pH? If it’s a meter, has it been calibrated recently?


On a pH chart for cannabis in soil, you’ll see that Phosphorous is one of the more finicky elements. It has a narrow pH range within which the plants are able to use it. Foliar feeding is best done at lights out, because it can act as a lens and magnify the light hitting the leaves, burning them.

My advice would be to double check your meter or method of measuring. If you’re certain of the numbers, I would flush them, then pot them up into containers like I described above. They’re gonna be pissed about it, and look like shit for a day or two. But then when they stretch their roots out into the fresh soil, in the right pH range, they will practically scream thank you. Look at the new growth for improvement. Damaged leaves won’t heal. Leave them until they’re falling off on their own for now, they need all the solar panels they can get. :v:

p.s. - for their age, they don’t look that bad, overall. Most of what you see will be shed weeks before harvest.


I did the slurry test today on two of the plants and found the soil pH to be 5.4 and 5.5. Is it normal to need to raise the pH of Foxfarm Ocean Forest soil?