Great Value Automatic Toilet Bowl Cleaner Tablets with Bleaching Action, 3.5 oz, 4 Count

I have used these tablets in my toilet bowl for hard water stains and build up ..going on 6 years I guess. They used to work great !! When I first started using them . During the yearly kill k I'llear or more, they have stopped working as will Fir example:::: 1. They no longer work cleaning my tank as before. They used to keep in crystal clear and gleaming white . Now the build up remains even when a new tablet is dropped right In the back of the tank. 2. When I clean the rest of the tank while the the tablets have been freshly dropped in the tank, I have to scrub really hard. Back when I first got the tablets, the tablets cleaned the entire tank by themselves. 2. My hands no longer sting after handling one . if the tablets. The have lost their strength.