Just opinion, but it looks like from the picture that there isn't very much perlite in that coco. That might mean the coco is staying too wet. It looks wet, but that might be right after you watered them. Maybe you could add some hydrogen peroxide to your water or aerate your water before you water them. Oxygen is important to the roots. You say you don't run to waste, but is there a way that you can see what the ph and ppms are coming out?
I've had plants look like that from over-watering, ph lock out, nute burn, and gofer eating the roots. From what you're saying, it probably isn't nute burn, or ph lockout, and pretty doubtful that gofers have gotten to your roots through your pots, so if you're getting good run-off readings, then maybe the next time you transplant, you add a little more perlite to your coco and get some rooting powder on those roots to help soften the transplant shock.
Another theory I have has to do with not running to waste. Does that mean there is no holes in the bottom of your pots? If there is still sitting water in your coco then you could have something eating your roots, Could be bugs, mold, fungus or some other funky junk. That would warrant a flush and transplant to new soil. Just opinion.