Could it be... HPS? I'm talking about your light btw.

NOOBS take note: if you just throw seeds into some soil and hope for the best this is what happens. Hell, I'm surprised you got this far. You have pH problems. The buffer is probably well depleted in the soil but of equal importance the pH going in is off too. Don't bother putting soiltabs into the pots. Get a pH meter and do it right. You will need to repot them if they've been in there 5 - 6 weeks. And you definitely need to learn about what you are trying to do.

Read "A Beginner's Guide to Growing" in my signature. Read it all. The whole thread. When you're done with that read some more. Better yourself with knowledge. Why don't people on these boards do their own homework? Sorry steveat, I don't mean to take it out on you. I just see a lot of people asking questions that would be obvious had they done even some basic background work...