It depends. I expect the PKI that was generated by the quickstart expressInstall process will contain only IP address and hostname (not external FQDNS). If that's the case, imo, you should remove everything and redo it. This page shows you the process. It's just rm'ing the files that were produced during expressInstall and unsetting env vars to make sure they don't cause problems the next time you run it..
If you have an external DNS available, it's always best to use that and ensure it's used in your overlay. Yes, you could make a surgical change to the PKI but to be blunt, if the network is still young the work to replace the PKI correctly is a lot more than just resetting/rerunning the expressInstall imo. If it were me, that's what I'd do. Yes, sadly, I'd recommend you reinstall the additional edge router too.
The key fields to look at are in the controller:
- edge -> api -> address
- web -> name: client-management -> bindPoints -> address
And routers at:
- ctrl -> endpoint
- link -> listeners -> advertise
- listeners -> address
Those fields should be accessable to anything participating in the overlay. Often that means "internet available" but it's not strictly required to be internet availalble... (I think usually that's what people would want though, particularly when starting out)