Looks like possible heat stress...what are your temps and how close are your lights? This might help a bit for self diagnosis if you can't get help right away.... http://www.growery.org/2991/Diagnosis
85 degrees, and 50% humidity. My wife just told me the tent got hot today for about 15 minutes.(90 degrees). Found out my fresh air intake timer is not working.
I get the same thing on my seedlings and young plants, I use a shop light and I put very close, but after I get them off that light they do fine, not a huge worry.
Yeah man seedlings don't need the full on HID, like Japan said a couple CFL's is plenty good for the first couple weeks till they get some true leaves. =)
Shit...didn't know you had a 600w on those babies!!!! lol When you get your cfl's make sure you get bulbs with 6500k for vegging....they can go within an inch or 2 as they don't produce a lot of heat.