well, considering the covenant and the unsc didn't discover any of those rings before they got to the ark, i suppose that no one would have been on any of those rings to release the flood, so the flood on those rings would still be in hibernation if the rings were still intact and wouldn't be breeding. but i think that there are two possibilities about the other 5 halo rings:
- they self destructed when the ark was destroyed
-the unsc went around the galaxy with the sanghelli and nova bombed the last few rings, destroying any flood inside them that were hibernating. if i was the person planning the destruction, i would also keep an unmanned surveilance done there with weapon systems to destroy any of the lucky little floating flood buddeyzz
anyway, thats just what i think