I agree with Jamie and Debbie ... A
sudden change in diet is not good for a chinchilla ...
slowly weaning him off or down to one or two raisins a week, is, in my opinion, the best way to go. I give mine cranraisins and papaya for the fiber and vitamins they each have to offer a chin.
Nuts can not be properly digested by chinchillas ... their systems are not made for that. Over time, the natural oils from the nuts will usually cause a chinchilla to have a fatty liver, which can, and often will, be deadly for a chinchilla. Removing the nuts from his regular diet is removing fiber ... but ... hay can be used to add fiber back to his diet. A chin should have fresh hay in his cage at all times.
Small dry poops may often be a sign of dehydration or illness. If need be, you might consider feeding him water with an eyedropper several times a day.
Yogurt contains the flora (natural live bacteria) needed to keep his digestive system going properly ... in most cases. I will often give my little ones yogurt with blackberries, or strawberries or blue berries in them. Dannon puts out an individual size yogurt container ... this will help in the costs. I let mine have as much as they want, if there seems to be a problem ... and often as a preventative about once a month.
The amount of liquids being taken in by your little one can also affect his/her health and poop. If you start seeing the outline of his spine, dehydration is almost a definite under most circumstances and should be addressed properly, a.s.a.p.
Please keep us posted on how he is doing.
Jo Ann