I have a Rhode Island Red that I adopted with 6 others in her flock last year from a man going through cancer treatment, and I am not sure of the ages...I have had them for a year, and they were laying when I took them They have been a great flock and are producing well. For the last two days one of the hens has been staying to herself, with her feathers puffed up slightly. She is out and about, eating and drinking, but just looking like she doesn't feel right. Tonight, they were all walking with me and two of the others were pecking at her and treating her meanly. I understand pecking order, but I have not seen them act this way before. If she is ill, would the others know it and try to isolate her? Any help would be appreciated.
Hen is acting strangely
Sounds like she is quite ill. By the time we notice, they are worse that we would think.
IMO you need to isolate her to a safe "hospital" ASAP, do a thorough examination and post what you discover.
Make sure she is drinking and eating. And watch her poop for more clues - and add that description as well.
Once the others realize she is sick, they will try to kill her.