@marvosa Thanks for the follow-up. Not sure what changed, or if I'm just impatient... Before I posted that last comment I had enabled dhcp for VLAN 300 and everything worked. Then I disabled dhcp and reconnected the external dhcp server and it didn't work. So I posted the comment and went upstairs and ate lunch.
Came back downstairs to continue troubleshooting and everything is working using the external dhcp server.
Thanks again for your help.