Seems like a very reasonable growth rate. Just to give you something to compare to I'll use my female pinstripe as an example. She was hatched in early July (I don't have an exact date from the breeder as she was a Repticon pickup). She was 75g on August 7th.
Here's her monthly growth:
8/7 - 75g
9/7 - 105g
10/9 - 165g
11/9 - 215g
12/7 - 245g (this 4 month growth seems right in line with your 4 month growth)
1/5 - 335g
2/2 - 380g
3/2 - 485g
I'd say you're doing just fine.
i should start weighing my BPs once a month to see progress.