Are they all the same age? Assuming they 'came out' as chicks....they are getting bigger so yes more crowding.This issue has been going on, on and off, since they came out to their outdoor living area about 3 months ago but it seems to be getting steadily worse.
Most likely coop is too small for 6 birds....larger roosts might help.I'll post pictures tomorrow when I have a chance to take some but the coop is about 4 feet by 4 feet feet and they have 2 roosts that are about 4 feet long each and are made out of 1x2 (it's what came with the coop).
Waiting for pics.......