My 9 months old male chinchilla is really light weighted. Is this normal?

Hi, I am seeking help about my newly adopted boy chinchilla. He is almost 9 months old but weighs only 383g. He does eat normally (mainly 1st cut Timothy hay and a small scoop of Mazuri pellets each day). He drinks normally too (I give him boiled water that cooled overnight). I give him dust baths (PUIK Chinchilla Dust Bath) about 2-3 times a week. We live in Singapore. I keep A/C on for him 24/7 so he is in temperature around 21-25 degree C with humidity around 50%-70%. I want to take him...

My 9 months old male chinchilla is really light weighted. Is this normal?