We are having a terrible first time experience with raising backyard chickens. Spent lots of time and effort setting up a coop and raising 3 chicks. First issue we encountered was that 1 of the 3 turns out to be a rooster. Found him a new home, but wanted a larger flock than just 2. So went back to the local chicken shop and picked up 2 hens that were about 3 months old to add to the flock. Then, one by one, we have had chickens get off-balance, lethargic and ultimately die. Almost like clock work each week, one more would get it after the prior one passed. We took the first one to the vet and it was determined she had an "infection" (not determined whether viral or bacterial), but the antibiotics did not save her. The second one died before we could even get her to a vet. The 3rd we immediately started on the remaining antibiotics left over from the 1st, but she died after appearing to make a rally. So now down to 1 hen who so far is not appearing to be sick (although it has only been a few days since the last death). My question - what to do if she lives? Is it cruel to keep her alone? Can we ever consider introducing more birds or is she carrying something that will infect future mates? Thanks for any advice.