It does indeed sound like you could possibly have a male in the bunch. I started noticing my drake "coming to age" right around three months. I had suspected well before then that he was indeed male. While my other four Pekin's would quack, and talk all day long, he would more or less sit quietly all day, unless it was feeding time, treat time, or I had changed out their water. When he did "speak up" it was always a raspy sort of sound that was much deeper, and not quite as much of a "honk" as the females produced. About 4-5 months is when his drake feather came in.
Next time you are out there, pay close attention to your ducks as they are talking, note, does that one talk much, and if it does how does it sound compared to the others.
I do have a bossy female that will on ocassion bite and pin the other ducks if they don't appear to be doing what she wants them to do.
