I would just go really bland for a little bit, and let your system calm down. Foul smelling stool can indicate a serious problem, but since it's not every time, it seems less likely it's that and more related to something you're eating. Still, you should get it checked out to make sure you don't have an infection.
I'm not sure if you were trying to boost your immune system with the superfood powders, but there's really no such thing as doing that. Most people's immune system is fine just by eating normally.