These are the email responses I got from Chris:
"OC doesn’t protect from water spots appearing. It only keeps them from etching below the surface like they would if the minerals were left on regular cleat coat. Water spots frankly are a complete reflection of the process and maintenance practices of the caretaker...not your installation, not Opti Coat."
"Water spots are 100% a result of allowing mineral rich water to dry on the surface. As the water evaporates, the minerals are left behind and will stick/bond to the surface...any surface (even a coated surface). What OptiCoat prevents it the permeation of those sometimes acidic minerals below the surface. To remove these deposits you must use a dedicated water spot remover (chemical non abrasive). To prevent these deposits you must not allow tap/sprinkler water to dry on the surface. The chemicals used to remove water spots should not harm Opti Coat if used per instructions and too much pressure is not used as to scratch the coating."
After my OP, I talked to him again and he said his town is known for hard water and the water was quickly drying before he could dry it all with the MF. I asked if if could try using some QD to see if the spots would come off which he said yes, the QD is taking the spots off on part of the hood where he tried it. So it sounds like just some light mineral deposits from hard water. We agreed he'd leave the rest there until I could look at it tomorrow morning, and so he doesn't mar the OC all up rubbing on it too hard. I will take care of the spots (won't take long if QD is taking them off) and I will show him how to properly care for it (don't use plain water, don't wash in the direct sun, etc.) and I will leave him some ONR to try. I will update after I get done with this tomorrow.
Thomas, I know what you mean that I should charge to fix it, but as long as it's not a huge chunk of my time, I would rather just take care of it and educate him on the proper care some more.