We have a variety of hens that we got as chicks this past spring. We added two to the flock in Oct (to make 11) and things were going well until recently. One of the new hens was staying in a nesting box day and night. We thought she was sick, or broody and isolated her for day. Gave her calcium and warm bath. She ate well, drank water and pooped. Later in the day the flock was out of run freeranging and we took her out and almost immediately one by one they all came after her. She retreated to the nesting box and has been there since. Any advice would be most helpful. We do have a light that comes on for several hours in the morning and in the evening the coop and pen. That is the only change I can think of. Help!