I'm guessing the water line stains are from the hard water. I used an old "PoolBlok" pumice stone on the 2 tiles in the first photo with the arrow. It helped, but once it was wet, I couldn't tell whether or not it was doing any good. Once it dried, you can see it helped. Using the pumice stone on just a few of the tiles really ate up the pumice stone (not sure how old the pumice was, seemed a little brittle to me to begin with). Is this the best way to clean this, or should I use diluted acid?
My wife was concerned about the plaster discoloration as well. Any ideas what caused this? Is this signs of needing replastering? I actually think it looks pretty decent. When the pools full, you can hardly see the discoloration. Both surfaces are pretty smooth and even. The really large dark areas are just still wet from draining.
Thanks. More photos in next post.