Either their roosts are too small in size(the mop handle) and/or there's not quite enough roost length for them.
I'd go with a bigger roost then you might have to force them in there for a few nights until the get the new habit down.
No, the coop isn't too big, it's barely big enough. They're getting bigger and may feel a bit crowded.
Definitively put in a wider roost, 2x3 or 2x4 wide side up.
Do you have good ventilation?