How much should she weigh?

Hii
So I have a 1and 1/2 year old female Chinchilla.
I'm worried that she is under weight.
Oortjies currently weighs 370 grams.
She has lost weight since March and I don't know why. She eats regularly and a lot as well.
Unfortunately my parents said they can't afford to take her to a vet.
Any advice?