Suyin is the one of mine who behaves like your hens. She was always out of the run foraging, hardly ate anything I provided [not even extra protein], & is super skinny. She drinks a lot ~ more than anyone else but she is eating better now she has finished her moult.Lots do eat normally apparently. I don't know the heavy moulters here can't do the same. It's a bit worrying when they don't seem to be getting enough to eat.