Just going to throw this out there. Do they free range? Is there any type of debris in the yard. Like cigarette butts or plastics? My hens tried to eat the plaster stuck in buckets i was rinsing out. But a hen ate a cigarette butt once ( from the hubby) and her poop looked horrific for the next few days. Im vigilant about them now and the hubby (if he knows whats best for him) is too. I hope she gets well soon.