My barred rock hen who is about 7 months old couldn't stand up the other day. That was one night, then the next day she was fine. A couple of days later she couldn't stand up again and has been laying on her side since. I tried to get her to stand up but she couldn't support any weight on her legs and immediately fell down. She can move her legs and wings but doesn't do so very often. I brought her in the house to get her away from the others and so I could keep a closer eye on her. She eats and drinks well and seems alert. She has diarrhea that really stinks. What could this be and what do I do about it?