Droopy leaves need advise

Not sure if this is the right spot for this question. A couple of my plants are starting to get droopy leaves. Aside from over and under watering what else can cause this?

I water once every few days. I use a meter to check the soil moisture level. I don’t think they are over watered and I don’t think they are over watered. Since both problems have the same symptoms how can I determine which is actually causing the problem?

Pictures would help, natural light, or flash.

On extremely hot days my plants would lower their leaves 30mins before lights off and rise up for the lights 30mins after the lites are on. I hear outdoor plants do the same. BTW your plants look fine

Mine would drop at night then once the sun came up. Meaning the lights turned on about 30 minutes later they would raise. The past few days they have been drooping bad. I started thinking maybe they needed a bigger pot? So I just transplanted them into a little bigger one. I was using the smaller ones because I had planned on getting auto flower seeds but did not. You think they look ok?

How long ago did you transplant, it took mine a week to adjust

Have you been feeding them or using potting soil with slow release fertilizer? I’m not on expert on what is wrong but the leaves look furrowed to me, if that makes sense. The leaves aren’t smooth, but have deep differences between the veins and material between the veins. Just doesn’t look right to me. They also look to be a little stiff/crumbly to my eye, but that is certainly hard to tell from a photograph.

I think it was the pot size. Today they look great