Is something wrong with my duck?

He's about six months by now. When he walks, he runs into walls and other objects. His quacking sounds weird. And he runs away from me. My other ducks love people. Is it just because he's growing that his quacks are changing from chirps to quacks? And why is he so clumsy? Nothing is wrong with his pattern or anything. Three other ducks from his litter died when they were chicks. Is he traumatized or something? Sorry for so many questions, but my other ducks didn't do this last year, they were little angels.