Marble dusted walls feel a little slippery

[jon123]

The walls of my gunite/marble dusted pool feel a little slippery.
When you rub the surface with you hand, you can actually rub this away, but you also get a little cloud from it.
It looks like your actually rubbing off the marble dust.
Is this possible? I was told low ph can cause this.

Thanks for the feed back.
Jon