Day 24 plants are sagging a little, do I start nutrients?

I have 2 plants, under a 150watt hps and a 90watt led UFO, they are in fox farm ocean forest and it's been 24 days since I first dropped them seeds in the water to germ. Anybody have any suggestions? I just watered them today before I took that picture.
Thank you in advance

What picture??

Just added it^^^

First of all they are rootbound; you need to upcan them ASAP. You should be fine on the nutes; they should not need any right now unless the yellowing on the bottom leaves continues after you upcan them, then you'll need to top-dress them with some blood meal or other Nitrogen amendment.

Do you have holes in the bottom of those cups?

I would consider transplanting them into a proper, larger container. It looks like its from the water.