Which of the Nutriphase Gold formulas are you using?
. I am using nutriphase gold pellets that contain a variety of other munchies and timothy hay.
I have always found that it is best to use a high quality chinchilla pellet that does not contain "other munchies". The "other munchies" are often what you would use as treats. Treats, hand fed, are much more pleasing to the chinchilla in most instances, because it has your complete and undivided attention when you are giving them to him/her. To be the center of attention is often wanted more than the treat itself. Also, most chinchillas, like children, will fill up on the treats and leave the things that are good for him/her.
Fresh grapes may cause gas, so I will not feed my chins grapes ... the grapes in a raisin form are OK and do not seem to cause gas. Always be cautious about using dried fruit, many times they will contain preservatives, unless you dry them yourself.
Dried rosehips and dried papaya are very good for them and contain lots of vitamins they need. I will also let my chins have a few nibbles of fresh banana as apposed to dried banana chips. They will take a nibble or two and chew the banana while grinding their teeth in appreciation.
They seem to like the banana most when still very firm and not over ripe.
Jo Ann