Switching to rat pups from small mice was the turning point for my current baby. She didn't do much for the first month and a half I had her. She would gain a few grams and then lose it when she went to the bathroom and she really didn't gain but about 15 grams in a month and half. I thought something was wrong with her but I really didn't stress much because she was eating, pooping and shedding. Once I switched her to rats she really started to gain weight. They were like fertilizer. lol