CR Blue Kote will keep the wounds from being noticeable to the other ducks even if they don't pick on the duck, I never said they would cannibalize another duck like chickens will. Lets just drop this. Hopefully the OP has taken care of her extra drakes and her drake that was plucked is on the...
TSC has it and maybe your feed store get the bottle with the dauber though because it's comes out purple and stains anything it touches I have better control with the dauber it's Gentian Violet that makes it purple that is why it disguises the wounds so well.
I'd give him at least a week separated but where everyone can see him, and get some blue kote it helps heal and disguises wounds so their won't be any pecking of the sore area.
Drakes can be so mean to each other poor boy.