My chinchilla is barely eating!

I've noticed my chinchilla Nunu, has been throwing out the food pellets for 2 weeks. He tries to eat the food pellets, but he ends up dropping it or throwing it away. My other two chinchillas, eat the pellets just fine.

He seems to be getting thinner, slouching more often, bites on my hand much lighter than he used to, and is slower than before.

From my own observation, it seems he has some mouth pain going on, since a few months ago, I've noticed he squeals at moments, while in the process of chewing the food pellets. Now he exhibits behaviours, that would show pain in a chinchilla. (Droopy ears, stationary and squeals).


My mum refuses to take him to the vet, claiming it was old age, it's too late, waste of money, or the doctors/vets in New Zealand are stupid, and can't fix anything.

What could be the issue with my chinchilla? (My assumption is that it's his incisors, though I can't tell if his teeth are the issue.) Is it too late to take my chinchilla to the vet now? What sort of remedies can I do at home to help relieve my chinchilla?

I really don't know what to do to help my little Nunu feel better.