Anyone know how to clean a stone shower?

[m&m's mom]

I swear I live in a cave. Almost every surface of my house is either wood, granite, or Italian Travertine Marble.
Well, the shower is entirely travertine marble -think not shiny marble but stone w/ slight natural pitting on the surface. We must not be that good drying it out because there are small sections that have mold on the stone. I have absolutely no idea how to clean this type of stone.
I have tried Kaboom, Scrubbing Bubbles and bleach (OK, I was desperate).Nothing has worked.
Any ideas?

 

[floridaminnie]

found this http://www.thetiledoctor.com/maintenance/cleaningstone.cfm

did you seal the stone?

 

[m&m's mom]

found this http://www.thetiledoctor.com/maintenance/cleaningstone.cfm

did you seal the stone?

I bought the cave - uh, I mean house 2 years ago so I am going to assume it was sealed. It beads up quite well it is just like dirty feet on the bottom and small moldy stuff from the shower bottles etc that I can't seem to do much on. Fortunately the color is tan/neutral so it does not show everything.
Thanks for the link. It had some good info on it. I have to admit I have no idea what a "Ph" or "Neutral" cleaner is.