A different wireless network on your own setup? Is this additional Wifi setup to use Pihole? If it is, can you temporarily change that Wifi configuration to use another DNS besides Pihole (like 9.9.9.9 or 1.1.1.1), then renew the watch/phone DHCP lease?
We really need to know whether or not Pihole is a factor in this issue in order to provide useful help. The way to do that is test with Pihole involved (which you've already done) and test with Pihole completely bypassed.
As for whether DNS cache is impacting the issue, changing DNS servers on the client as previously suggested would remove the possibility that DNS cache is the cause.
so the solution was to upgrade my phone, no idea why it worked but I also ended up factory resetting my apple watch in the process of setting up my new iPhone so that might have helped