toes curled can't walk but can move legs, diarrhea

[the pampered egg]

My poor girl(RR) can not walk. She can move her legs but her toes are curled. She also has diarrhea (no blood) but otherwise she is bright and alert. Her comb is red, eyes bright, eating and drinking. I am giving her some electrolites. She is an old girl of 9 years. None of the other hens are sick. Any ideas of what is going on with her or what I can do?