I'm not sure if this will help anyone but it helped clear up confusion for me.
/etc/yum.repos.d/salt.repo had the [salt-repo-3007-sts] enabled=0 and [salt-repo-3006-lts] enabled=1, but my salt-master (and a majority of my minions) have 3007.1 installed.
So at some point the salt 3007 STS repo was enabled but it is not anymore. I do not manage repos that closely so I know I didn't make
this change.
Essentially my machines that were on 3007.1 were locked on that version because I couldn't download 3007.4 with the repo disabled.
The machines that didn't have 3007.1 installed were still on 3006.x so they upgraded to 3006.12. The "newer release" of 3006 is not compatible with the "older release" of 3007 so communication broke down between the master and minions.
Now I must either shift the machines with issues onto the 3007 STS branch or rollback the majority to the 3006 LTS branch. Lucky for me it looks like salt-master 3007.5 is capable of communicating with every minion, so I can use salt to correct the salt version and repo mismatch.