Red Rust

ROOT CAUSE:
Red in color, deposited from iron rich water as it evaporates
ANSWER:
Removed with acid, however acid will damage many underlying surfaces and grout, as such best addressed by a professional
SOLUTION:
If rust stains appear on marble, travertine or limestone call a professional as most solutions will do damage during the removal process which then need to be repolished or otherwise reversed to return a clean red-free surface.
Speak to an expert (888) 524-3372