We moved house last year, and the two toilets in the house have dark stains at the edges of the bottom of the bowls. I do flylady style swish and swipe every day, and have tried toilet cleaners and I even scooped all the water out of one and filled it with (cheap, admittedly) bleach in an attempt to shift the stains.
Nothing makes a bit of difference. The toilets are clean, so I'm not even sure what the stains are. But they stare up at me, mockingly, and I would like rid of them 
Any ideas?