This happens to me in all my fasts. When I started doing long fasts I had similar BMs as yours, in latter part of my fast. Then it started increasing. In my last fast I had BMs everyday, smelly, brown, sticky, stainy. I also feel so much cleaner, focused and energized after I complete the fast.
What you are experiencing is a good thing. I know that years of eating junk does not clear out in one day. I am a raw vegan and still see junk coming out.