what have you put in your water ? I think that is a sign telling you your LR is DYING .. it's white and turning brown. I've seen that happen when people put copper in they're tank
i havent use copper at all i dont even know what that copper thig is it look like to me a burnt peace of rock my other liverock doesnt have it but its just growing coraline algea idk what the brown stuff is HELP!!!!!