I have a 2 year old Buff that has been brooding off and on for months. I took her and two other hens that are also brooding out of the nesting boxes and put them in a separate small section of the coop I use to quarantine sick chickens. They were all fine and healthy when I did this yesterday. This morning the Buff could not walk without falling over. The other two chickens were just fine, no issues. It sure what is going on with her.