So for the last week or so I noticed little grey flecks in my toilet bowl after a flush. Thought maybe the bowl was dirty under the rim, and gave it a good scrubbing. After that did not change anything, I lifted the tank lid and the surface of my tank water looks like a pond (but not green).
There is a grey scum (very much like pond scum) all over the inside of the tank.
The toilet is only about 1 year old in a newly added bathroom in my basement. My wife did throw one of those blue hockey pucks in the tank about 5 months ago (that will never happen again after I found this site).
I can post pics tonight if it helps. I'm wondering if some part on the inside of the tank is slowly rotting away.....