Look here, could be (as already stated) magnesium deficiency or Ozone is also possible.

Marijuana Plant Abuse
Vancefish Reviewed by Vancefish on . Yellow Leaf Dots Spreading Completely Over Some Leaves (It's not spider mites) Hi All, I'm trying to diagnose this leaf problem. It's currently affecting almost every plant in the room, some significantly (half the leaves), others totally minor. It doesn't seem to have any pattern: the edge plants (least light, least heat) have it no more or no less than the center plants. I know there are a lot of factors to consider in diagnosing a plant problem, but maybe someone will know what's going on -- once they see the pics and read the post. The pictures show how it Rating: 5