Hi, I'm Pete. Welcome to JustAnswer! I'm reviewing your question now, and will post back with your reply ASAP.
These unwanted spots of colored toner will be caused by an issue with either the toner cartridge or the photoconductor unit.
If you have already tried replacing the toner cartridges then that just leaves the photoconductor unit as the likely cause.
Hi, just checking in on your question, do you need any further assistance?