looks to me like you have perhaps a few problems 1. over nute judging by the tips of a few of the leaves. 2. are you foliar feeding? perhaps pooled water burning leaves. Or finally have you inspected closely for mites?
I know its not spider mites, I religiously check for bugs twice a day after a nasty infection a few months back. Ended up having to bleach the entire grow room and kill everything.
I was thinking possible over nuting but the leave that looks like that is very rare on all the plants, I run quite a few in a room too, so its not that common (maybe one out of 10 plants has a few leaves that look like that). From what ive gathered on forums and the few years ive been doing this Nitrogen was what i was thinking.
Im foliar feeding with liquid light ... just cause ive had some laying around for about a year that i used previously.
pic 2 of 5 remminds me of a prob i had - mold - i had been sucking up mold from old carpets with my extractor - check your surroundings - watch out for moist areas near your grow esp carpets
worth a shout
I had a small problem with powdery mildew but thats been taken care of. Maybe 4 plants had a SMALL amount on them but they have since been treated and cured.
I know its not carpet because the room is full tile.
Thanks for the input guys, its appreciated.