I have six hens, four laying, one "retired" and one just gave up the laying habit (she's not old). All six have been cooping up at night just fine, but recently one of them has decided that three of the others should find somewhere else to sleep! She stands at the coop door and won't let them in. They have plenty of room, three roosts, they lay in the same box, they get along during the day. Right now the three who are left out are sleeping under the coop (the coop is on tall legs and it's about two feet off the ground). What should my approach be here?