Are they sisters? Its a common problem with sisters which is why its not really advised to keep litter sisters together.
Best advise I can give you is to treat them as individuals, walk them separately, train them separately and feed them separately. They need time apart and you need to create a different relationship with each of them, this will help their relationship with eachother.
__________________ Indy, Benjamin and Malachi   There is no psychiatrist in the world like a puppy licking your face- Ben Williams |