Well that orange and pink build up is normally either in the grout or around the door of stand up showers. It can also be found in grout on the walls of the shower, drains, sinks as well as toilet bowls. You may think it's just rust- but it's actually bacteria that likes and feeds off of moist areas. You can prevent this from occurring as much by regularly cleaning your shower/bath/toilets/sinks. When not using eco-friendly cleaners for clients I use Clorox bleach toilet gel.