I have realized over the past week when I pick eggs & feed & water my chickens that there is always 1 Americauna still inside pacing back & forth on the roosting bar. Even when I throw scraps & scratch out & the rest rush to it, she still stays in there. I noticed that the feathers around her butt look bad so I caught her last night & found that her vent was clear, but that she had a lot of poop built up & stuck to her butt. I pulled that off, but she went right back to trying to be alone. Should I be concerned there is something else wrong? It has been so cold & damp where I'm located that I'm concerned the chicken could be sick. I've got plenty of ventilation in my coop, but the atmosphere is just plain damp. I've been keeping a light on for them since the days are shorter, but have no supplemental heat source. Thank you!