Leaves spotting/curling/dying only on upper fan leaves help please (pics included)

Hello everyone,

I have 40 cones of critical mass under 1 600w and 1 1000w hps about 5 weeks into flowering. Using FoxFarm Ocean Forest soil in 1 gallon pots and the FoxFarm full line of nutrients including the 3 powdered micro-nutrient formulas. The problem started about 2 weeks ago when there was some brown spots on the leaves. It has progressively gotten worse and is is now like you see below.

I alternate every other watering with plain ph'd water and nute solution. I have tried flushing already but it has not fixed the problem. I also dont think it could be nutrient burn because this problem only occurs on the upper leaves. Mostly the fan leaves but it is starting to occur on some of the upper bud leaves as well. I also have a dehumidifier in the room keeping it a stable 40% RH. Temps vary from 60 at night to 80 during the day. Ventilation is good with a high output centrifugal, fresh air coming in through the window, and a large oscillating fan.

I have also thought it may be a problem with fungus knat larva or root aphids destroying the roots, so I have also performed a soil drench about a week ago consisting of a .04% Azamax and 1 pint of mighty wash mixed with 12 gallons of plain water. This also didn't seem to fix the problem as it is still getting worst. I'm not a novice grower and in all honestly I feel like a complete idiot. I don't know what to say. Any help or ideas would be much appreciated.

I think your main issue is that you flushed the nutrients out of your soil...so in turn you are starving them...hit em back and hit em hard...nute with every watering...you've got a bad magnesium deficiency it looks like...but in general you shouldn't have to flush unless you actually overnuted

Agreed, you do not need to flush and you have a bad magnesium deficiency. You need to add 1 tablespoon per gallon epsom salts (Magnesium Sulfate) at each water from now on following your regular watering schedule. To begin correcting the problem immediately you can dissolve 1/2 teaspoon epsom salts in 3 cups warm water, put in a sprayer bottle, and foliar spray the leaves down two hours before lights on. Mag def will affect yield, but not if you correct it now.

Thanks guys. I picked up some epsom salts and foilar fed and also some CalMag and will use 2x strength tonight. Will keep you guys posted on progress.

also note...you arn't looking to "recover" those leaves...they won't really recover...they are way too damaged...what you should hope for is it not getting worse here in a few days

Looks very def in K and P and N. Use the nutes every watering and doublecheck the ph is 6.5. Also it didnt help spraying pesticides/soaps on it either, only use this shit when you have got mites. Only flush with nute burn or salt build up.