I've been thinking its a Magnesium deficiency, but after applying the solution about 5 days ago, I still have no results (foliar spraying and top-feeding). Any ideas? Has anyone seen this before? Temperature gets no higher than 75, no lower than 68. Humidity stays steadily around the 45% range. I'm using an air-cooled 400w MH lamp about 8 inches off the plant. Fed reverse-osmosis filtered water, OREGANISM, and Roots Organics line.
The spots on the leaves looks like a Cal def. or a PH problem (which is what most def. start out as) Take a look for yourself: Cannabis Plant and Pest Problem Solver - Pictorial - 420 Magazine
It may sound weird but diluted urine (1:10 ratio) every other or every third watering during vegetation and diltued urine and potash during flowering (every week) is easy, cheap and difficult to burn your plants.
could be too much potassium. i'm pretty sure that could interfere with the plant utilizing magnesium too.
first guess is a ph issue that is not allowing the uptake up magnesium or another trace element. this would also explain why your solution application failed to provide results. somewhere in the sick plants forum i read that deficiencies are caused 9/10 because of a failure to buffer the ph to the respectible level to allow nutrient uptake dont quote me however. you didnt state if you were growing all organically or with synthetic nutes. Im facing a similar problem with my plant in mid flowering but the amount of humus in my soil would contradict the theory ive provided if you are indeed using synthetics nutes. hope i was of help in some way