I spotted mites before on a Corn I used to have and the 2nd Ball I ever acquired, spotted an RI in a Blood/Borneo mix I had and in my Dumeril's boa, as well as extremely strange behavior in an Albino Burm I was fostering to try to get her to eat (twisting of the neck, uncoordinated actions, etc.) which could have been caused from lack of nutrition or disease.
Although thankfully with quarantine I didn't see any of those symptoms spread to my established collection.
These snakes exhibited these symptoms in the first couple days to the first week of having them. Each were treated according to what they had, except for the Burm which I had put down because of the symptoms being similar to untreatable viruses and due to the lack of improvement during the time I kept her.
So, this means to ALWAYS QUARANTINE new arrivals. You never know what could show up and how threatening it could be towards your established collection.
EDIT: Also, none of those snakes had come from reputable breeders. That also shows you to choose wisely where you get your animals. The BOI is excellent for looking up feedback on breeders.