help , fubar plants (pics)

ok here is the problem , this is my 2nd grow the first went the same way yet I have made differences but obviously not the one I need !! 1st time around I used soil hand watered and used ionic nutes , the boost worked great but then they went the same way as these , just yellowed and died , so I started again got a 10 pot wilma because I was advised it could be over watering or nute burn I also highered the light in case it was leaf burn. These are the the same thing , they were fine on the night-time went out in the morning and they looked liked this , these have been under a 24 hour light - 600w and they have been under the light for 2 weeks tomorrow , they have not grown at all !!! I'm using coco with the canna coco nutes (just the a/b mix) what the hell could this be ??? one of the photos is really fuzzy but it shows the colour better if that makes sense , the other 2 are overviews

Welcome to RIU

NO NUTES for the 1st 2 weeks. Your probably juicing them up too much and then the 600w is frying them.

I start in rapid rooters until a good root structure is developed (about a week), plain PH'd water only. Then its off to the coco coir, plain PH'd water for about a week then nutes at 1/4th strength. I use flouros for the first week to get them used to light before zapping them with my 400w MH

Coco requires a slightly lower PH so make sure you are monitoring that. 5.6 - 5.8 is what I am using.

they has no nutes until they were 2 weekd old , they are now a month old , I should have explained that better it's been 2 weeks since they have been under the light , (they were under flourescent b4 that ) I thought the stronger the light the better as it has more lumens , (as you can tell I'm a noob) I started them off at half strength on the nutes , you might have a point with the light though I've tried everything else and hadn't thought of that !! lol , mind you it made no difference when I highered the light ?? would it have done if that was the problem , I also have fans and heaters to control the temp and that is as stable as I can get it. anymore suggestions ?? thankyou btw