I got three ducks 2 weeks ago, all about 1 year old. 1 male and 2 female. They were raised together and get along great. 3 days ago I got another adult female and put them together. She is so sweet. The other ducks don't like her and won't stop bitting and chasing her. She does not give up and follows them around everywhere they go. I feel bad for her. Is there something I can do to stop their bad behavier?