Yellow Pod leafs?

I have 4 plants in a 15gallon tote that I think are stunted. The pod leaves on one of them are pretty yellow...

DWC set up

its normal for the cotyledons to yellow as the plants use up the food stored in them. they are too small to really feed yet. are your pH levels in check? over all the plant looks pretty good, a bit light green but not too bad. if you have a decent root mass you could start them on a 1/4 strength nutrient solution.

Ye the cotyledons are supposed to turn yellow but those first set of true leaves are getting pretty yellow which is not normal most likely used all nutrients in cotyledons and needs some nitrogen and ye the ph is probably too high

Btw how old are those plants ?