Oh what did I do?

I have a handful of plants in 100 gallon smart pots that were all looking healthy and beautiful up until the day before last when some starting showing signs of some problems. Almost all of my plants have leaves that are yellowing, twisting and curling up with brown/rust spots. Some of the new growth on the tops of buds are also twisting.

The strains I have are Pot of gold, Blackberry kush, Grandaddy Purple, and Hippie Chicken.

I've been giving them water twice a week, usually 15 gallons a piece, feeding every other watering. Using all fox farm fertilizer with botanicare silica blast every other feeding and I've fed them cal-mag 2 times since they started to flower the first week of August. I use Tiger Bloom, grow big, and Big bloom as per the fox farm feeding schedule, all the solubles I have been using at approx. 3/4 strength, and the silica blast I use at about 2/3 strength when I use it. pH of the water is always between 6.4-6.8. I've been spraying with Spinosad about every 15 days as well. The weather where I am at has been in the low-mid 80's in the daytime, but dropping down to the 40s at night.. I have greenhouses that are being put up momentarily to deal with the cold at night.

I kind of can't kill these plants, so I figured I should seek some advice before I start fully diagnosing problems my self and trying to find a solution.

Here are a couple pictures of a couple plants that are affected.. All of my plants are showing the same problems. Sorry for the links. I don't have internet where I am at, using a slowwww data connection and my uploads keep failing after like an hour of trying.. Almost as frustrating as the problem with my plants... I have more pics and will try to post them later, but I need to get to some wifi. Like I said though, lots of yellowing on leaves, some are twisting, brown and rust colored spots on leaves..

http://imageshack.us/a/img138/3008/img2891tb.jpg

http://imageshack.us/a/img801/935/img2892dr.jpg

http://db.tt/qhXPeLhq

http://db.tt/HEbAaii9

That is hard to tell man. Looks like it could be from the heat or under watering. A notch more Mag and Nitrogen could help with the yellowing and brown spots but overall it looks good except for the withering leaves. It is out in the full sun right? How hot is it in your area lately?

The leaf edges folding upwards do indicate a pretty classic magnesium def... also its possible in full sun at the hottest part of the day it is too much for the strain, heat stress looks very similar. If you can add mag easily, I would try that first. If they dont respond, perhaps get some sun cloth. The larger hole kind that is just for lessening the intensity but not fully blocking it out. Good luck.