What's going on with these seedlings?

Please take a look at the pics of these two seedlings. One is Sweet Tooth from Barney's, and the other is El Nino from Greenhouse - both are 10 days old, growing under a 600watt digital HPS. I use FoxFarms Ocean Forest soil, and no nutes as of yet. In the pics you'll see some yellowing/discoloration around the tips, and the leaves seem to be dry and brittle in the affected area. Any ideas as to the cause? These are only 2 out of 15 total seedlings and are the only ones experiencing the problem. Also, my room stays at 77F with a RH of 35-40%. The temp directly below the light stays between 78F-82F. Thanks for any help!

anyone got any ideas?

I'm new to the game, but perhaps that light is too much when they're so little? A lot of people I've read start with CFLs or the like. I could be way off here, just venturing an idea?