diverinva
LR can have many different colors of coralline algae, purples and pinks by far being the most common. This orange-ish brown color may be due to several things.
When did you set up your tank - how old ?
How long have you had the rock in the tank ?
Do measure your pH, alkalinity, calcium and phosphates ?
If so - what are these levels ??
Will help us to try and answer your question