Mysterious Smell That Irritates Eyes?
Have your a/c ducts inspected... could be mold.
Toilet Scratched By a Plumber's Snake?
Currently have this problem and will try Barkeepers. I caution against the pumice stone. It may take the marks off, but it also scratches the finish off the porcelain, making it more likely to stain in the future. My mother-in-law used one to remove hard water...