how far away should a 600w hps be from 3 week old 8inch tall clones

how far away should a 600w hps be from 3 week old 8inch tall clones my room is 1.2m square

if the clones are already rooted then you can get the light as close as you can without excessive radiant heat. put your hand at the top of the plants and lower the light as low as you can with your hand being comfortably warm but not hot. if you have an aircooled hood you should be able to get the light to within a foot.

they are rooted they have been for 3 weeks and been stunted with all leaves turning yellow seems anything i put in there is turning yellow any ideas wat it could be thanks for any help

could be lots of things. ph off, too much fertilizer, too little - check out the diagnose problems link in my signature