Plants are stunted

Hey all,

Ive been growing these in a phototron 3. Their growth seems to be stunted. The tallest one is 4 inches. I started them in 1/2 potting soil 1/2 soiless mix.
Ive feed them rain water only PH 6.8. They were doing fine till last week, now, not much growth and some yellowing but not much. Also notice the red stems on some of them. The plants have started to curl their leaves and some look droopy. The smaller plants are only a week old, the larger are 3 weeks old do these seem small?

Do you ever PH the run off?

No but I definitely will. I should mention that I only water them every third day. Thats when they dry out. The temp is 81 to 60 (for 6 hours dark). Most of 18 hours its 74 to 77. Humidity is 30 to 40 percent.
Im just using the phototron to veg till they can go outside. I was wondering if my container is too shallow. They're so small I didn't think it would be an issue.

hey can you tell me how to start a tread

I think you have some nutrient lock-out going on. The plants seem have a deficiency and being so young it shouldn't be the soil so the next thing to check is PH as that can cause lock-out. Maybe your soil is very high or very low ph. You can tell be comparing the runoff Ph to the water ph.