Must the prayers that were performed after the cessation of bleeding from an internal mouth wound be repeated, given the presence of a taste of matter exiting the wound that was not noticed until after the prayers were performed?

The substance coming out of a wound (be it water, pus, or serous fluid) is impure. Your prayers are valid as long as you were unaware of the presence of this impurity. You are not required to repeat the prayers you performed while tasting the wound's substance in your mouth.