funny, a buddy of mine has the exact same set up as you. and just got a bunch fo clones last week

well a 1000W (hps or MH) is very hot for little guys. How far away do you have it. you should have it at least 2 ft away. The heat causes them to loose water quickly.

What are you temps like? Try to keep below 80 F. dont worry if you cant. I cant seem to most of the time. But dont let it get above 85.

a good idea might be to move the light far away and mist them. Then move the light back close when the waters gone off the leafs. you dont want to burn the leaf. Make sure the mist is very fine, no beading.

You can also try to increase the humidity of your room. HAve a few buckets of water around. it all helps. It seems to me that they are just drying out. No worries it happends. But they can die very easily when they are so young.

you should have your lights on 18/6. IMO
What i do, is give them a small amount of water several times a day. And i only water were i know the roots are. ie the rock wool.

Pictures help