2 year old male only 300 grams?

[Bodie]

I don’t think he’s a picky eater because he has an amazing feeding response. I think his previous owner was just underfeeding him for whatever reason.

Sounds like it was good you guys found one another Now that you got him, I won't worry about the weight. If he is eating great for ya and the meals are the appropriate size (which it sounds like with weened rats at that weight), he'll be alright. Sorta sounds like he was underfed, but at this point the past doesn't matter. Good luck and I'm sure he will put on some weight for ya.