Hi Bonnie,
there are a number of theories concerning feather picking, one like you mentioned is a lack of protein (which you can remedy by adding extra to their diet). Another is boredom, you can try various techniques to keep them busy like hanging cabbages etc. In my opinion the quicker you deal w/the problem the better. Once a habit has started it can be difficult to break it. You could try separating the offender for a couple of days. Or you can order rooster booster's "pick-no-more" lotion, it works well, you put it on the bird being pecked and it pretty much takes care of that bird. I've had this problem in the past usually in the winter months when the birds are bored and confined more. I always add extra protein during these months (via gamebird feed), but to be honest this never fixed the problem. The only relief I found for my birds was the lotion mentioned above.

Hope this helps.

Sheila

Here is a link that might be useful: Rooster Booster