Has anyone had stone guard problems. Our set decided to deposit what I will describe as algae on the paint under the guards. Regular rubbing car wash would not remove this stuff. I thought at first it was just I hadn't washed the car often enough, but after about three washes and the same problem we replaced the stone guards. We had waxed the guards always washed when washing the car - yes they were the original set - guessing about 8-9 years old. To look at the guards you can't see anything wrong with them. Scrubbing the gunk off the car wasn't any fun! Has anyone else had this happen? PS car is garaged at home and covered parking deck at work - daily driver.