My hen, a 7 year old Ameraucana, is very ill. Her eyes are swelled up, one more than the other. She's very weak, has lost a considerable amount of weight, and has diarrhea. She is too weak to get up on the perch, and she has been sitting on the ground. She is eating and drinking. All of my other hens seem perfectly healthy, it's just her who is very sick. I don't know what this is, and I would greatly appreciate some help. I'm very worried for her. Thank you, Montana.