Seedling leaf fading and die back

These are pictures of a strawberry cough seedling that are in a half Roots soil and half Promix mix, and the older leaves are starting to fade and die back at the tips. This plant is currently growing under a T5 HO florescent with temps in the low 80's. Any feedback on what might be happening here would be greatly appreciated. I've had this happen on several seedlings and I'd like a solution to stop it from happening

Well, I'm not a soil grower, but to my eye those cups look awfully small to be growing a plant with 5-6 nodes. I know what root structures look like on a plant with 5-6 nodes (I can see it in hydro) and those cups look really small to me.

Perhaps it's time to transplant to a proper sized grow pot?

Other than that, maybe your nute solution needs tweaking? You haven't said anything about ph, so that might be an issue, too.

On top of what he said above, I don't know if you just watered that cup and that's why the leaves are drooping like that.. But too much water and subsequently not enough air in the soil can cause leaves to do that. I'd take kryptoniteglo's advice and consider repotting and easing on the water to give your plant some chance to breathe down below. I'm only a new grower, but I had a seedling doing that from too much water.

Thanks for the responses guys. I'm gonna see if transplanting helps and I'll start to let the soil dry out more then I already do. Im going to be transplanting into some of subs super soil, so I'm trying to not use any chemicals and only use water. I may try adding some compost teas throughout the lifecycle however. I believe the ph of my well water is fine, but I haven't checked officially so I'll look into that as well