Feather plucking - supplements?

[chickndays]

Chickens are feather plucking. All but one (Australorp) has a bare patch at base of tail. The worst offender seems to be a Rhode Island Red. It went right up to a dust bathing chicken (same breed) and started pulling out and eating feathers. I don't think this is the head chicken but it seems to be acting high up there.
Also have silver and gold laced Wyandottes to illustrate breed colors. (The gold laced has a bare bottom)
Which vitamins should I try to supplement to their feed?

 

[FrostRanger]

I would switch to a higher protein feed, preferably one with 20% protein.

That said, in addition to that you might also need to jail the worst offenders for a week or so and/or put pinless peepers on everyone to break the habit. Also how big are your coop and run in feet and for how many birds? Pictures of your setup would be helpful as well

 

[thecatumbrella]

I hate to be the bearer of bad news, but reds are notorious for feather picking (guess how I know!) What feed are you using (especially protein %)? What's your setup look like? Are they free ranging?