Situation: 4 hens (3golden laced Wyn and one barred rock...no rooster) they have been together since birth 10 months old....coop is 6 x 8 with attatched large run but the girls free range all day. When I locked the doors tonight I noticed a huge amount of downy feathers all over the coop....a lot...the barred rock and 2 wyn were on the roost but the 4th one was in a nesting box.All eggs collected earlier. She seems fine...no injuries...so I left her there. Just went out three hrs later and she is still in the nesting box. All 4 girls always sleep together on the roost and I have never seen any feathers other than a single stray once in awhile. Why would they suddenly single her out or do they just get mad at each other like that?