Ron, my experience has been that chickens eat feathers when they are low on protein. They also go through a molt at around 9 months and need more protein during this time. There are several things you can do when they are stressed like that. One of my favs is to get a bag of game bird starter, which is high in protein, and mix it into their regular feed, some folks start giving some small dry cat food, but you can also scramble up lots (depending on how many are in the flock) of eggs and feed it back to them, maybe even mixed with plain yogurt. Treatments like this should slow down the feather eating.
teatimelady, your issues are more of a pecking order problem. If left on their own, they will gang up and kill the poor girl. I would bring her in and cleanse any bloody spots. If you have some blukote, just spray some on the wounds. If they see the blood they will continue to peck but if it is covered, they'll leave it alone. However, the pecking order problem will remain and get even worse when you put your girl back with the others. If you have lots of hens and only one or two are causing the problem, then separate the trouble makers for several days, to give them an attitude adjustment, then put them all back together. Hopefully, they will loose their dominance in the flock and stop the pecking. This is a much more difficult problem than Ron's. Good luck.