spies, I would love to know if the vinegar works.
Besides protein problems and lack of space, bordeom is another big factor, assuming this isn't hens picking the rooster. I have 7 rescue hens that spent a year in a guy's bedroom, and when I got them last spring at a year old, 4 were looked so ratty from the picking. Picking stopped within a few days of getting to their new coop, as outdoors, lots of space, lots of other chickens, etc helped.
The picking problem just reared its head again, though, I think because they have less outdoor space that they will use with the snow - they tend to stay under the coop - and because they are sometimes reluctant to go outside if I am not home to shoo them out - again becaues of the snow. during the work week, I leave and return home in the dark, so they spend time in a smaller space.
I am trying a flock block, and I've ordered something called rooster booster no pick lotion - which has juniper oil as main ingredient.