Update, just wanted to update people who gave advice. Exactly 3 weeks after this post the next mother gave birth to 16 pups. And about a week after that, the baby that I had held back from the first litter, even though she was only 2 months old, gave birth to 11 pups. Then the original mother 2 weeks after that gave birth again to only 2 pups(shes getting old). So my production finally took off. So four litters and i'm averaging a little around 9 or so babies each litter. I would be averaging a little over 12 but one of my rats is getting pretty old. Thanks to all for the great advice