First of all, how is his feces look like?? Are they just look like normal, or become small, soft or even liquid form??
If the feces carry bad smell, most probably your chin is facing some digestive system problems.
Another important things is that does your chin willing to take grass hay at the moment??
My friend have a experience of over take of unsuitable food. The case is he forgot to close the cage door properly, the chin go out without his attenetion. He also own a cat, and normally his cat cannot finish all the cat pellets, so most probably his chin have taken lots of cat food as he find the cat bowl is empty. After his get back the chin back to cage, his chin refuse to consumpt the regular chin diet and the feces become small and smelly. And at last, his decision is to cut off the chin pellets and only offer timothy hay, luckly, his chin start to eat the hay after a short while and recover soon.
If your chin refuse to take his regular diet, it is very danger and can be fatal even for a short while, as chin need to intake fiber for their digestive moment. I would suggest your chin to have a VET visit if he really refuse to eat anything. Or if you really cannot visit the VET and have no other way around, if I am the chin owner, I will cut off the chin pellets (pellets can be a burden for the digestive system for an ill chin), just offer lots of Timothy hay.
On the other hand, feed with Critical Care or Critter Be Better in order to increase Probiotics in the digestive system and bring the gut mobility back to normal. You can also mix a weak glucose water to him because if your chin is facing soft feces, it is easy to make a chin to "dry out".
What I suggest should be a very mild and safe way to recover you chin, but a VET visit is always best for your chin.
(I am not a English native speaker, so I only try my best to express my suggestion, hope your chin can recover soon)
