
Chinchillas love a routine ... when the routine is changed (or caregiver changed) they will often cut back on their food because change will often upset a chin's system. Many times, chins that go to a show, will not eat anything during the time they are gone from home ... change in regular routine.
How much weight has this little one lost? To be able to see/notice the change, there must have been a drastic loss of weight.
Is the spine noticeable?
Does the poop smell bad?
A "yes" to either of the last two questions would be cause for a vet visit. Better to be safe than sorry.
Keep us posted, please.

Jo Ann