I use Mean Green on EVERYTHING! I swear by the stuff actually. I'll have to find that Krud Kutter....I could certainly use it here (we have hard well water as well).

Whatever you use...don't spray it directly on the spots. I'd spray it on a wet rag and after that I'd wipe it up with just a wet paper towel dampened with plain water to wipe away the residue to prevent a fire or something.

Best of luck to you!