Soap Scum Issue

I have a black cultured marble shower pan which developed some "white" spots that I assumed were soap scum. I tried severeal different cleaners but have been unable to get rid of these spots. Any advice on a good cleaner that can help in this situation?

Thank you,

Jerry

I'm not a pro or anything but I absolutely love Mr.Cleans Magic Erasers.They are very soft and do not scratch.What do others think of that?

Those really are magic! I use them to remove ball point pen marks from many surfaces. I think this would be a good first shot on the cultured marble.

Thank you very much for the information. I'll certainly give this product a try.