My guess would be that this is not about regular feather picking but the young cockerel with raging hormones trying to mate an unwilling and immature pullet. This will be stressing the pullet as well as losing her feathers. Even if you get rid of one of the males, the chances are that this will continue with the one you retain as the pullets are not ready to mate and two to one cockerel is a bad ratio anyway, especially when they are young.
A solution might be to build a bachelor pad for the 2 males. They should live together reasonably peaceably if they don't have any girls to fight over. Or of course to get more hens..... with it's associated responsibilities and risks and logistics.
I have no experience of pinless peepers and whether they would work on overly amorous young roos.
