What sized mice are you feeding?

In my experience, I've found that feeding multiple smaller items on a 7 day schedule has yielded excellend growth. I too got a hatchling in August which I feed 1-2 rat fuzzies, about the same amount of food as 1-2 small adult mice. I do this every 7 days, and that hatchling now weighs about 320 grams.

The rate of growth you mentioned is fine though, everyone does things differently.