Wots wrong with my babies

Can anybody tell me what problem i have here. I have 4 skunk #1 clones in bcuzz coco inside a "hydrogrow skinny" tent (75x75x180) with a 600w hps lcooltube. I have a 5" fan for extraction and a 4"fan for the intake. they are 3 week old and growth has been really slow. I've been using canna coco nutes A + B at 1.5ml per ltr of water. I first encoutered he problem about 1 week into veg so i decided to flush them, they seemed 2 have recovered in a day or too bt as soon as i started them back on feed its just got worse. Can anybody tell me what they think is happening here and how to sort it. This is my second grow everything is identicle to the first, but the first one went spot on with no problems whatsoever

You are using grow nutes right? I screwed up one time and gave mine bloom nutes and thought it was the other way around.

Trust me! Everytime ya grow something different happens. Different problems and shit.

To me they look like they need a good dose of nutes.