Return of green poop?

I have been dairy/soy free for 3 weeks now and I know that it can take even longer than this for milk/soy protein to get out of my system and DD's system. However, DD has had normal brown/yellow poops for the last week to week and a half with a sudden return of dark green, runny poops the last 2 days. I haven't made any dietary changes and there's no accidental dairy I could've consumed (I've cooked everything myself). If I need to continue on the list of top allergens to remove from my diet I will, but it just seemed like the dairy/soy elimination had fixed the problem. Is it normal to fluctuate while getting it out of our systems or do I need to look at eliminating additional foods? Thanks for any advice!