Yellowing clones... Help please

I received clones from a reputable source and they arrived fresh and rooted in rockwool. They were transplanted into seed starter pots with Roots Organic Original soil. They are under a 600w MH with temps around 70 and humidity around 40%. I have put some over them and left it cracked open for air circulation. But it looks like I'm getting some nitrogen deficiency issues. I have FF grow big but since I'm trying to grow organically and have EWC in the soil, I don't want to kill my microbes with a big dose of salt or or burn my clones. Any thoughts on how to remedy this quickly and safely

Yellowing is normal with new clones. Relax. Let it recover, and grow it's roots back. Be patient young padawan.

Thanks! I always thought that the curling tips was a heat stress thing. I've never had low temp problems in any of my other grows. This is also the first time my clones have gone yellow on me like this. First was from seed. 2nd from clone which were hardened off and grow outdoors at a friend's house, so I'm going for 3rd's the charm