Poor thing, you and the Ducklings, I would have thought any preditor would have eaten at least one, even if it were a rat!! Maybe a cat has got in and been playing with them, so strange and a funny place for them to be injured, I wonder if they have been pulling out thier own or each others feathers?
? I am very new to DUck keeping, someone should be able to advice you fingers crossed...maybe, in the mean time, you shold move them!!!