My toilet was running, it turned out the flapper inside looked like it was starting to deform and squish together (the top part of the seal was no longer flat against the bottom of the toilet. So I went out and purchased a new one and installed it. Now 3 months later my toilet is running again, I open the back and the brand new flapper looks exactly like the old one did. Starting to looks almost like it’s disintegrating. (hope that makes sense) anyone have any ideas what would cause this? I do have one of those bleach tablets in the toilet, but I have them in my other toilet and this has never happened.

Thanks