whats causing this

You can't really expect people to just solve your problem with that amount of information, but here's my 2 cents worth. Some yellowing is normal, especially on those two initial leaves. Sometimes they don't yellow though. Are you growing in dirt? Did you use ferts? I hope not. In hydro? Did you use full strength nutes? I hope not. Too much light on those youngsters is bad. Is your light too close? Too much heat will cause yellowing. What's your grow room temp. Do you have ventalation on them?

and how can i fix it
Yellowing other than normal yellowing is usually a nutriant problem. If this is the case, you need to flush with PH adjusted water as much as you can handle, then feed with 1/8 strength nutes if in hydro and no nutes if in dirt (for 2 or 3 weeks). Why don't you look at the plant problem chart I posted under "you need this."

Decent digital cameras are like 50 bucks now.