I relocated a temperature probe on my K-Rims system and had to disassemble several parts on my Spike BK & MT. I noticed what appeared to be rust/staining on the threads inside some of the NPT couplings. Unfortunately, I didn't capture a picture before putting everything back together. There was a post by someone on this site who mentioned "sugaring" but I'm not exactly sure what that means and if it's anything to be worried about. Should I be concerned?