I have a four-year old RIR hen that has been pooping light green. It has not been bad, and she is eating/drinking/walking fine. However, I noticed today that the feathers around her butt are messed up with runny poop. The only thing that has changed recently is that I had one older hen die a couple of weeks ago, and she was wheezing so I treated the flock's water with antibiotic for five days. That's about the time the green poop started. Any insight would be greatly appreciated, and should I separate her?