Benzelsanswered grow question 3 years ago U went from a seedling light to a real grow light and now the plants have responded by exploding with new growth and they are a little bit hungry, thats all. The older leaves look fine so its likely just very fast new growth and the color will come in over the next few days, if not then try making your next lot of nute mix a TINY bit (like 10%) stronger and start changing the res a lil more often too if your going longer periods between changes.
But honestly its not really a problem at the moment, more a watch and see and maybe tweak things a touch type deal here ok. Not a problem. Plant looks REALLY nice other than that so it may need slight tweaking to dial in, but its NOT a problem. Dont go changing things alot as that will make it into a problem. Small changes IF, and only IF it doesnt improve on its own in a few days ok.