what kind of coco are you using? I see in your description your using water with a ph of 8.0? si this correct, it should be at 6.1 or 6.3, that would give you symtoms like this, did you flush the coco? even with botanicares coco which is one of the best you have to flush the coco with phed water, mostly to get those salts out, not to set ph. Coco is the way to go in my opinion, add some nice nutes and your good to grow.