Hello and thanks for researching this very important question!
In many species grinding the teeth is an indication of pain. Refusal to eat in Chins is quite serious. Shedding can be related to time of year, reduced nutritional status, stress or illness.
There are a number of things that come to mind with these symptoms...including, but not limited to:
1) Chinchillas that run free indoors can get themselves into things that can cause intestinal blockage...rubber bands, plastic bags, carpet threads, etc. This would be diagnosed by an xray and would require surgery to correct it.
2) Intestinal infection...this condition is quite painful and can cause death in a relatively short time after signs begin. Prescription medication is required for treatment and cure.
3) Hairball impaction...shed hair can be swallowed and cause a blockage condition similar to case #1 above. Some mild food/hair balls can be treated with a bit of juice from sauerkraut, but do not delay seeking medical help if symptoms continue into tomorrow.
4) Females can develop uterine infections...needing immediate medical attention to prevent systemic exposure to bacteria. Sometimes a bloody or heavy discharge can be seen from the vulva.
Symptoms of pain should be addressed by a qualified veterinarian right away.
Here are some additional reliable articles about these problems:
http://www.veterinarypartner.com/Content.plx?P=A&A=666&S=5
http://luvnchins.com/HintsForNewChinParents.html
Time is of the essence with the "pocket" exotic pets, so I am including these links that help locate veterinarians familiar with guinea pig and rabbit medicine...these vets are often able to diagnose and safely treat other small exotic mammals, but do let them know what species you need to have examined:
http://www.cavyinfo.com/html/vet.htm http://www.aracnet.com/cgi-usr/seagull/vetfinder.cgi http://cavyspirit.com/vets.htm
If you need additional support at this time, please click "Reply", otherwise I thank You in advance for your "Accept".
Retired Veterinary Technician
Dog, Guinea Pig, Hamster, Gerbil breeder / Reptile Keeper / Bunny-Ferret-Exotic Specialist