My young hens almost stopped eating and sit in their nesting box all day

Ive got 3 hens about a year old. They were broody like 2 months ago which was expected. They went back to normal, everything is fine. But since a few days they seem to eat less, poop less, are very inactive and just sit in their nesting box all day. They are sitting plump with their tails up a bitike when they were broody. They havent layed eggs in over a week where before i would get one a day of each of them.

I havent found any lice, they seem in a normal mood when i pick them up or give them treats. Their coup is clean, their food hasn't changed recently, they get plenty of fresh air in their coup and have outdoors area to roam around. No stuck eggs in their behind, no watery bellies or full crops.

What am I missing? The only thing I can think of is that the weather changed here recently from below 20 degrees celsius to almost 30 but their coup and "yard" are almost fully shaded. I get them plenty of fresh water everyday as i expect they will drink more but I cant think of anything else that may bother them.