What Causes Brown Vaginal Spotting While On Herbalife Tablets?

I recently starting taking diet supplements called Herbalife tablets total control, multivitamin, cell-u-loss and cell activator, along with a healthy meal shake once a day. I'm 24 years old, 148 lbs, 62 inches, and have been on birth control for 9 years and have never really had an abnormal period. I started brown spotting a week before my expected period and am wondering if could possibly have anything to do with my changed diet.