Brown stains on stairs??

[MaryLee]

Ok....everything has been great up until now...

Chemistry is perfect for my level of CYA (CYA 30, FC 2-3, pH 7.2, TA 100)...18 X 40 IG Vinyl.....crystal clear water

Tonight I noticed that the stairs and skimmer plate below the water line is turning brown. It doesn't rub off......is this a metal problem???

I haven't filled my pool since the day it was initially filled in 2004. Once in a while I'll add and inch or so from my well when there's a hot spell or a "cannonball" party, but for the most part, the rain fills the pool up (and I end up draining).

Any advice on how to deal with this brown staining on my white stairs..should I be testing something or adding something to the water other than bleach??

Thanks in advance!

[MaryLee]

Oops!! Sorry...just realized we have a whole section on metals and staining....I'm off to do some reading!