Light gray ring around toilet’s bowl. How can it be remove? I tried Lime-away and CLR (calcium, lime, & rust remover in liquid) Still there, even after brushing. It will come off in flake by scraping with tip of a screwdriver but will try to leave metal marking on surface. Is some sulfur (southern Florida) in water supply will have anything to with it? Any suggest be greatly appreciate. Thank you! Have a great day to you all with U S of A Flag Sojourner for Christ Jerry Sr