No one seems alarmed at that size. 12" = 30cm. This 9-month-old BP is only little over a foot long! Aren't hatchlings close to that size?
Astral, if the snake really is 9 months old and only 35cm, that's very small. Try to weigh it. At 9 months old mine was 400g and about 75cm, and others are bigger. Is it very thin? If the shape of it is like a round circle, then it's good. If it's narrow, more like a triangle, that's VERY thin.
Don't worry about making it fat, as it sounds like it's starving at the moment. Feed 2 fuzzies every 5 days. It should soon fill out, and then you can move up to the next size. I feed mine 2 adult mice for a total of 40-45g.
Good luck!![]()