A week ago I had a chicken die on me very suddenly. Today I went out to feed them and one of my chickens was wobbling around as if it's legs were bothering it. We isolated her and gave her some antibiotics. Now, this evening, another chicken is beginning to show the same symptoms of "limping". The one chicken we have in isolation can stand, but she more or less lays down most of the time. Any suggestions on what's happening to my hens???