Help, recurring plant issue

This has really got me stumped. I was having a problem early in the grow, but was able to solve it with the help of the wounderful member of RIU but now its back and everything checks out okay. My PH is between 5-6 (hard to get an exact reading because its a kit), my ppm are at 1200 spot on. At first i thouht it might be MG, but i have been adding 1-2 tsp per 1 Gal of water, That dose not seem to help. I have Been using GH floragrow, floramicro, florabloom, and i know that they lack a bit of mg, however no luck. They are at about 1 week into flowering. I thought it might be heat stress but the top leaves are fine, the problem seems to be at random affecting the bottom leaves the most. here are some pictures.

No one? Anyone have an idea?

Is it effecting most leaves ? or only a few on each plant ? If it's only the odd leaf here and there i would cut the leaves in question off and see what happens. How are the buds forming ? do they look ok ? in general does the plant look healthy ? If it does i would not worry this can happen from time to time.
Sorry for all the q's just trying to come up with a solution.

It seems that it's only effecting 3 leaves from the top of the plants (one per plant) and maybe half a dozen of the bottom leaves. Its still to early to tell if it will be effecting the buds, but one of my plants did herm, Now if it was the seed or caused by stress, i don't know. The plants seem healthy apart from that. I'm just worried about causing the plants too much stress.

Out of my 5 Plants, 2 have Herm, I discovered the other this morning. Damn it. Not sure if its Genetic or stress. So now I'm Down to 3 Plants.