I have 4 16 week old chicks. My speckled sussex started to start something new yesterday. She will put one leg up and freeze, as if to scratch, but looking more like she's having a seizure. She'll try to get the other leg up there, too, causing her to fall down in a screaming pile of chicken. She seems like she is in a lot of pain, but I'm not sure what to do for her. I have checked for any sign of mites or lice all over her body and see nothing. Other than these spasms, which are maybe one an hour, she is out with the other three chicks, eating and drinking and hunting as if nothing is wrong. But she seems like this isn't normal... any suggestions? Possible respiratory infection?