I think Mazuri rocks
glad to know he is feeling better! I have heard that Mazuri pellets make chins have smaller and sometimes softer poops so if you notice them a bit smaller don't worry. The food on him is okay, like Gray said use the washcloth. How long has it been since his dustbath? If its been a while you may still need to give him one, try having it with an open container and not for too long. Watch him closely.
Another thing I do with my chin (even tho he's healthy) is give him 500mg of Vitamin C once a week. I give him the chewables I found at walmart and he loves them!
I think since you had the fiesta mix (I know which one you're talking about) your chin picked through and ate all the yummy stuff that he shouldn't be eating (like treats). Many companies claim stuff is good for chinchillas but isn't; another good example of something to never get is that 12" 'chinchilla' exercise wheel from Petsmart. Every chinparent learned day by day :-)