I have two baby rats, 4 and 6 weeks old. They were always slick and thin and suddenly, within a day they were chubby. Kind of bloated and round. They are behaving the same. Hyper, happy and loving. Just more round. I feed each of them a piece of dog food a day because the breeder recommended it...as well as rat blocks (blocks of processed rat food) and carrots. Should I change something in their diet? Are they ok? I've been massaging their bellies in case it's something not passing through.