Help! Poultry problem!

[Welshies]

I don't have chickens but I have ducks but PLEASE HELP ME.
My ducks are 10 weeks. One has started to pluck feathers off of the others so the others become raw. It is doing it constantly now, and they have wounds. This duck has an adequate diet and space. None of the others are doing this.
What can I do?

 

[sourland]

Separate the duck that is doing the damage from the rest of the flock until they are fully feathered.