I have a Drake toilet and, like other toilets in our home, it is starting to develop a small pink ring around the water line. This can be cleaned with a brush, but will then reappear in about 10 days weeks or so. In our other, non-Toto toilets, we have installed a Fluidmaster Flush N' Sparkle system, which works just fine and eliminates this problem. Will this system, which contains bleach, damage the special bowl on the Drake? If so, are there other recommendations for permanently eliminating the pink ring around the water line?