If your bp isnt gaining weight you may want to increase the size of his or her food. Also this is a matter of debate with some people but I would try to switch to rats as soon as possible. Eventually you will have to change over or buy stock in mice. The sooner you can get them to start taking rats the better. They also have more nutrition in them for the snake. Rats will also help him get some weight on him sooner. That I know from expereince.