We have 4 Mallards that are almost 7 weeks old. One of them is constantly pecking the other ducks, sometimes plucking a feather or 2. While I am seeing no significant harm to the ducks yet, the others are agitated by the behavior. It did it the first 2 weeks we had them, stopped for 2-3 weeks and has now resumed. The other thing we've noticed is that the "mean" one is the only one that will ever swim in the pool we made for them. They all used to LOVE swimming and playing in that water! Any suggestions?