Chin's stool is loose

Hello Everyone,
I am a new chinchilla owner, after intensive research. We just got our male chinchilla (Chilli) about a week ago. We got our chinchilla from a petstore, I tried to adopt but there were none available in our area. I kept the food pellets the same as they were using in the store, according to the sales rep. We were feeding him treats, such as dandelion drops (fed him two and after reading about them gave them to a hamster owner), cheerios, a bag with mixed nuts and fruits, and oats to have him warm up to us. He seems to be a young chinchilla, based on what I can tell and the store rep. Now a week later he has loose stool, they are sticky and sticking to his fur on the bottom. We did get him a larger cage, so he was moved (not sure if this could be a factor) I am not sure what to do and what is the best options for him. We have discontinued the treats (as of today, we just noticed this) but are there other options and suggestions to try to ensure he stays healthy. Any responses and suggestion will be greatly appreciated for the new addition to our family.
Thank you.