brown discharge on consumption of fresh fruit/veg?

I have been on a "flush" diet so to say for the last five or six days and am only consuming fresh vegetable juice/mix, fruits and also commercial drinks like v8 and soy milk. Since yesterday I have been noticing my panty getting stained with a brown discharge from my vagina. It can't be the onset of menstruation bcuase I just finished my last period on 3rd Jan and my periods have always been regular.

Would anyone have any clue if this is indicative of something? Would really appreciate advise coz I feel confused.