We noticed a few days ago that one of our chickens, a year-old black tail hybrid, was limping. Since then, her condition has gotten worse and worse, and shows no sign of improving. When she stands, the toes on her right foot and curled under her, and her leg sticks out backwards. She can't really walk anywhere without falling over, so she just sits down. She's still eating and drinking, though she has diarrhoea. If we pick her up, she'll just about try to perch on our finger with the toes. Help please!