Today I noticed several members of my flock (including the roo and cockerel) bullying one hen. I've had this hen for 2 years with no problems. My flock is generally harmonious. This didn't seem like a small scuffle - every time I moved one aggressor away another one either tried to peck her or puffed up its chest at her. She has been healthy, eating and laying (right now she's taking a break as she's just finished a molt), sleeping and hanging out with the rest of the flock. Are the other birds sensing an injury or illness that I can't detect? I've got her in separate quarters. Should I keep her there while I'm monitoring what's going on and if she seems healthy try to integrate her back into the flock?