John & Amy are right. Chinchillas are not created to eat fresh fruits and veggies. If you study their habits in the wild you will see that even there they eat dried vegetation. Since their bodies are not made to digest wet foods, fresh fruits and veggies will indeed cause sickness.
It has also been proven that chinchillas are the most healthy long term with the blandest diet. It takes them awhile to learn to process new foods (which is why we have to slowly wean them onto a new food). Its important that we keep this in mind when we are feeding treats as well.
We are very strict with our chinchillas' diet. It is so hard not to spoil them with lots of different treats, but its our job to make them as healthy as possible. So they only get their hay and pellets and a supplement. Our pets do get one treat a day but we stick to only one type. We will give raisins, dried papaya, and rose hips but we don't go back and forth between the two. The get a raisin every day until the box is gone, then we may switch to papaya and again they get that only every day until its gone, ect.