My opinion (as a mug) is the brown is most likeley rust from your hot water system, indicating that it is probably on its way out....
Have a look at your unit and see if there is any visible rust staions down the side of the unit.
(Keep using it to get the nice wintery looking fake tan look from your shower.)
A plumber or sparky could replace it....or I have known people to DIY a simple swap out for the same size unit.
M