my soil kinda looks shitty like that too. My most mature plant has gone through hell. Approaching 3 weeks. It has yellow cotyledon leaves and the tips of my first real leaves are yellow too.

I'm worried it might spread up the leaves soon. I put them out in direct sunlight before i got my lamp and they roasted. I recently overwatered them expecting high UV but it wasn't bad that day

It hasn't been all that hot here in WNY but the UV ray's have been horrible.

My suggestion would be to keep them shady or non direct Light if your temps/UV are high right now where you are. I have Fluor tubes now but i'm worried between the overwatering and recent exsposure it will get worse.

Can yellow leaves turn back green? or at least stop yellowing? or is it too late by the time it happens, espcially this young?