I have three brown leghorns that are about 20 weeks old. They haven't started laying yet but I expect them to start soon. Over the past few days, one of the girls has started acting very timid. She doesn't appear to be sick or injured and I haven't seen any of the other chickens (11 total including 1 rooster) bully her. She is eating and drinking and will come out to forage occasionally during the day. She just seems to want to be alone. All of our chickens free range. Any ideas what this could be about?