Okay, so i've done a few things since last post.

I kinda figured this might be a case of calcium deficiency. (Hope im right :wtf So I added 10tsp of MagiCal to my res. (per instructions on the bottle) And started a weak solution of Nutes. I've also, for the past 2 nights, sprayed an even weaker Nitrogen solution directly on the leaves right before lights out.

The large plants seem to have stopped yellowing and are growing very nicely. I did notice a little browning on the roots (but this is only at the water line, and i think it has to do with the color of the nutes, which is a dark brown) They seem very healthy otherwise.

I trimmed the a couple of the worst leaves off one of the plants.

Im going to hold off on the H2O2 until i get a response. I read that the 3% solution you get from the store might be a bad idea? I'm also curious, but now kinda think its a bad idea, if spraying a diluted solution on the roots is a good idea. Input? If not, then how much should i add for a 10 gal res?