To update my situation, my chick that made a miraculous recovery had a relapse about a week later. I separated her from the other chicks when she was barely stumbling, and I started the vitamin therapy again (poly-vi-sol, vitamin E and selenium), but she got worse and worse for 9 days until we decided to put her down. She couldn't stand at all the last few days, and the last day or so she was so weak that she couldn't even make a stab at her food. She couldn't move much at all, and I found her flipped over once. I feel bad that I let it go so long, but I thought she might make another recovery like the first time. I should have put her down weeks ago when she first got sick.
I would like to send her to my state animal lab to figure out what was wrong with her, but our vet warned me that Maryland is a bit heavy handed - she told me this when we were discussing whether or not I should have a raccoon that my husband shot tested for rabies. My vet told me that the state would make me have all unvaccinated pets put down, including the feral cat that I had just dropped off to be neutered and vaccinated. I would like to know if my chick had Mareks, failure to thrive or some other sort of virus or congenital disease, but since this was the only sick chick I had, I guess I'll just let it go. If my other chicks start getting sick I'll deal with the state lab then.
I would like to send her to my state animal lab to figure out what was wrong with her, but our vet warned me that Maryland is a bit heavy handed - she told me this when we were discussing whether or not I should have a raccoon that my husband shot tested for rabies. My vet told me that the state would make me have all unvaccinated pets put down, including the feral cat that I had just dropped off to be neutered and vaccinated. I would like to know if my chick had Mareks, failure to thrive or some other sort of virus or congenital disease, but since this was the only sick chick I had, I guess I'll just let it go. If my other chicks start getting sick I'll deal with the state lab then.