Please Help! Black/Brown discolorations on leaves - Ends drying n dying (gray color)

8 - White Queen Females (3 month indoor veg) 3 foot
Medium - Miracle grow Organic potting mix - 2.5 gallon
Lighting - 120w and 90w UFO 3w & 1w LED + All around spot CFL's 60w (18/6h cycle)
Temp - 68-78 F (72-76 F avg.)
Humidity - 35%-65% (50% avg.)
Air Purifier - 100w industrial grade deionizer
Ventilation - 1 14' Push fan (IN) Push cross run from air purifier 1 14' Pull fan (OUT)
Nutes Organic Dried Blood 12-0-0 (1/2 tbs per plant)
Dyna-Gro Bloom 3-12-6 (1/2 tsp p. gal)
Dyna-Gro Pro-TeKt silicon solution 0-0-3 (1/4 tsp p. gal)
Tonic SUPERthrive (3 drops p. gal)
Foliar Mix of 1/4 tsp. DG bloom - 1/tsp. DG-ProTekt - 1 drop SUPERthrive - Mist before lights out daily

So, the plants were totally beautiful for 2.5 months and just recently in the last 2 weeks have they started to VERY rapidly deteriorate.

Two weeks ago I faced a massive fungus gnat infestation (which seems pretty solved) - I first flushed the plants to bring larvae to surface and hit them with a heavy dose of azoltrol post flush - I then used a light Foliar neem oil spray on leaves. - I completely wiped/vacuumed/sterilized the inside of the tent, including fans and lights and set up those yellow sticky traps

Week Later...

Leaves are curling in and black spots are appearing on lower leaves, Head to hydo shop - Im referred to some of that organicide Fungus? or Leaf Septoria suspected? - Wait a day and do heavy dose of Organicide 3 including foliar spray (heavy) 3 days... Leaves continue to wither,curl,black spots - aka dying...

I really thought it was leaf septoria since it was affecting mainly the small lower to mid branch foliage - So... I buy neem oil and copper soap spray - do a heavy spray in the evening 3 days in a row... Still no results just getting worse...

I'm really concerned at this point and any realistic professional advice would be appreciated.

Here are some pictures of the leaves that im taking off daily.... must be 100's now... HELP!

Please really take a look at picture 3 - Thats slowly what every leaf is starting to look like on every plant... Black/Gray spots - end drying out/crispy/dying

The last pic is how the worst plant looked just 2 1/2 weeks ago...

simes said:

Two weeks ago I faced a massive fungus gnat infestation (which seems pretty solved) - I first flushed the plants to bring larvae to surface and hit them with a heavy dose of azoltrol post flush - I then used a light Foliar neem oil spray on leaves. - I completely wiped/vacuumed/sterilized the inside of the tent, including fans and lights and set up those yellow sticky traps

Click to expand...

This is a classic grow shop sell-u-till-the-plants-are-fracked thing.

Next gnat infestation just dry your soil out almost to the point where the plants wilt, and put some sand on top, about an inch or two thick. The gnats will lay their eggs in the sand as is their habit of laying eggs just under the soil surface, and then die in their own cycle time. The eggs will hatch as they do, but will also die since the sand is dry. The worst thing you should do is dose root areas with heavy chemicals, this will send an otherwise healthy plant into root shock and could bring on deficiencies as the shocked roots try to recover from the megablast of chems.

simes said:

Week Later...

Leaves are curling in and black spots are appearing on lower leaves, Head to hydo shop - Im referred to some of that organicide Fungus? or Leaf Septoria suspected? - Wait a day and do heavy dose of Organicide 3 including foliar spray (heavy) 3 days... Leaves continue to wither,curl,black spots - aka dying...

Click to expand...

And in perfect form the hydro people sell some more crap which they caused in the first place with the overkill of the gnats. Sorry to speak in this manner, but I do get a little agitated when I hear these stories time after time....I do know though, for you the grower this is no fun position to be in.

simes said:

I really thought it was leaf septoria since it was affecting mainly the small lower to mid branch foliage - So... I buy neem oil and copper soap spray - do a heavy spray in the evening 3 days in a row... Still no results just getting worse...

I'm really concerned at this point and any realistic professional advice would be appreciated.

Click to expand...

Your plants are suffering a combination of root shock from the chems used to kill the gnats, and all the other oils and chemicals (orgnicide 3) sprayed on the leaves. Each one of these foliar sprays leaves a thin film of residue on your leaves starving them of co2.

The key clue here, and is almost always the case, is that prior to the grow shop advice to gas your plants with their chems, your plants were actually doing ok even with the gnats.

Now I am not saying that there is not some fungal things going on there, it is hard to tell when there are a combination of causes at play, but at the very least no more chems on the leaves or in the soil. The copper should have dealt to any fungi if there had been any in the first place, which I doubt.

You are probably not going to like this piece of advice but its the best thing I can think to say in this situation.

The best thing you can do is to wait it out, get real regular with the feeding and dry periods, and leave them to recover in their own time.

Meanwhile you probably need to answer the first question that never was asked, how did the gnats get in there in the first place?

Start by checking your soil pH if you haven't yet. Pictures 1 and 2 are showing Calcium &/or Magnesium deficiency. Pictures 3&4 are showing Phosphorus deficiency. That combination of deficiencies can be caused by a pH of about 6 when it should be 6.5.

Thanks for your advice, what your saying now that your saying it seems to make more and more sense....

Even with the massive gnat infestation and them sucking the life out of my babes, - they still looked "healthy"

I did have one more question do to some rather condescending input on the part of this websites chat room - Some users stated well first im a total noob - thanks to you for your brief display of unempathy towards me and my children - but that tangent aside... miracle grow organic potting mix, they said was the underlying culprit - I wanted to ask is this possible? or just trite meaningless 2 cent input considering the plants were thriving for the better part of 3 months... Once again thanks...

- I already did a soil/foliage (what remains) shower/flush to try and get some of that crud off the plants... You said lack of CO2 - should i water/spray them with some club soda?

Thanks again - Simes

The best medicine for your plants is no shocks. Their are terrible creatures of routine and while they can take the odd shock, cannabis will fare badly with lots of over treament. In hydroponics your reaction time needs to be immediate, but then again that is because the environment can go pear shaped in a matter of hours. pH can spike, drop, EC/PPMs can swing, nutrient temperatures rise, pumps fail, and all that requires that the grower 'must do something now to fix this', or plants die.

In soil its the very opposite. Rather than the environment changing rapidly and the grower needing to repond, its often the grower that has changed something rapidly and the plants need to adjust and get back into their routine. So the tendency then is to apply the hydroponic method, try something, if there is no immediate change, try something else, plants get worse, try something else, and so on. In soil it is often the 'trying something else' that has the worsening affect on your plants health.

Your plants started out well, then the soil got infested with gnats. The threatment for the gnats as recommended by the grow store has resulted in multiple changes in the plants environment, and a half a dozen or so shocks to their system and the plants have reacted accordingly, by going into shock, and as a result their nutrient uptake has slowed, probably leading to a food deficiency. So the advice comes in to feed them more calcium and magnesium, probably the two culprits in this case, but yes that is what the plants may be deficient in, but that is not the reason why they are deficient as there is probably no shortage of calcium and magnesium in what you are feeding them.

Remember, they were not deficient before you started the bug treatment. The bug treatment regime did not strip calcium or magnesium from the food you feed your plants either.

The deficiencies come because the plants have received multiple shocks, they themselves have stopped or slowed in their uptake of nutrient probably because the soil is phytotoxic from the anti-gnat chems.

Get them regular again, water them, let them dry out, feed them, let them dry out, and they will again start to uptake nutrients.

Jamming more calcium and magnesium in the soil is not going to make them get over the shocks that have caused them to slow their uptake, that will be fixed when they get back to their routine.

Hope this helps, and sorry it doesnt give you something that you can walk into your grow space and fix....type advice...but its the best advice I can think of for your situation, and in fact 9 out of 10 support requests I read on RIU.