One of my girls started looking ill some time back, weight loss and almost no appetite. At the time I had isolated her and after around 10days or so she was doing better and no one else was ill so i let her back with the flock. She's been fine until the past week. She started looking weak and droopy again, was skinny and had taken up residence in a box with a broody hen(to stay warm). I KNOW I should have culled her yesterday but it was Christmas and i thought i could put it off until today. Well when i went to check for chicks this morning she was dead. I removed her, checked everyone else out but everyones fine, even the 3 hens she's been snuggling with. I still don't know what happened to her. I guess I am looking for some reassurance for the rest of my flock? If it was ONLY affecting the single hen it was likely genetic or something that she ate maybe? Everyone else seems fine but I am still a little worried. Also have new chicks and more hatching in the coop so I am concerned for them as well, especially because I'd like to rehome them.