I have two chickens, an ISA Brown and a White Leghorn. The one I'm concerned about is my Leghorn. I noticed her sitting in her nesting box and thought that she was only laying an egg. But then after an hour, she was still in her nesting box, and not even leaving for food or water. Her vent is red and inflamed, and it looks like she's been pulling her feathers out. I don't know how long she's been like this because I only noticed it today. Her crop and abdomen aren't swollen, and she has no problem with the other chicken, and the other chicken has no problem with her. Any ideas???