One of my four Australorp hens, who is otherwise very healthy, has an olive-sized knot just under the bottom of her breastbone. A scab has developed, and it is oozing around the edges. Some feathers in the area have been pulled out, I assume by her pecking at the sore. Any ideas about what I can do? She is a one-year-old hen who has a very sanitary coop & run, and she is allowed to forage outside for at least an hour every day.The other three hens are perfectly healthy.