I have a hen that is about 4 years or older. She has always gotten along with all of my hens. I only have 3 hens and 1 rooster. For the past 2 wks approx., she won't come down from the roost, won't socialize, and doesn't want to come out of the coop when I let them out for free range time. One hen has been picking on her, but nothing violent. No injuries. I don't know what to do because I have to go and take her down every day just so she can be by herself to eat and drink something, which isn't much, and then she runs right back up to roost and stays there all day. She doesn't look or act sick. Not sure what else to do. Please help! Thx!