Major plant problems please help

I'm not sure what's going on at all please help . The leaves on my young plants have turned very lite green and are curling under. I'm not sure how to proceed or if I did or didn't do something but they started looking horrible yesterday. Any suggestions or possible solutions will be greatly appreciated. If they are not showing signs of getting better by tonight I'm going to try to transplant into different pots. Thanks in advance and please keep all negative comments to yourself please.

Its tough to say exactly what the problem could be when there are so many variables. What have you been feeding them? What is the environment like? Post a picture, this way the readers can see if its an over all yellowing or maybe its just inbetween the veins. Add more description to get a better answer.

Thanks for replying think I got it figured out was a super trifecta lights too close, too low PH, and lack of N. Seems to be coming out of it now thanks again.

Hope you have them all dialed in.
Here's some late pointers (perhaps you already know) Be sure to keep your water PH balanced every time AND don't over water!
You said the plants were young. Be very careful with nutes if they are young. Best results and happy growing!