Problem solved. I had left the reverb effect on both mic channels instead of the group. Once I removed the reverb from the individual channels and put it on the group all worked as expected.
If I mute the group LR is muted. If I take the fader all the way down, LR has no volume. Muting does not fully mute the other mixes. Taking the fader all the way down does not fully cut the volume on the mixes.
