plants droopy and sad looking at night

I'm currently doing an outdoor grow, and am just starting to get preflowers. I check on the plants quite often, sometimes several times a day just to get a feel for how they are doing after feeding, before feeding, at different times of day, etc. I have noticed, time and time again, that the plants are drooping as if they've been overwatered if I look at them at night. During the day they are very healthy and vibrant, no spots on the leaves, no nute burn, no drooping, etc.

Is this common, and if so, does anyone know the reason? Is it just temp change, or do the plants go into some kind of rest state when the sun isn't shining on them? Are they just conserving energy because they have no reason to be sticking up like that if there's no light on them?

thats normal I had a big girl one that is my avatar she would slump over at night in the day she would perk up towards the sun there sleeping and using energy underground ....

yeah it's normal, for me at least