How do I solve issue of Premiere mixing down mono audio tracks in multicam sequence?

When I create a multicam sequence using a 3-channel mono audio track (recorded separately), it looks like the audio is being mixed down so I can't isolate the audio tracks. The first channel is a mixed down mono track then I have two lav mono tracks. After I create the multicam sequence, the audio appears mixed in the timeline.

I've tried created a new sequence and selecting 'mono' under the Tracks tab but I get the same result  - mixed audio.

I'm using CC 2017 on an iMac 2017.

Any help appreciated!