Another question for oxypowder users

In the beginning after starting Oxypowder , the stuff being expelled was very black which was a very hopeful sign to me. After just less than a week, the "liquid" is brown and I am a bit worried that all that is coming out is what I'm eating. Which is not my purpose! My last meal of the day is around 6:00 p.m. and I take the Oxypowder at midnight. Is this possible, that it could be food being eliminated and not plaque from the intestinal walls?