I reached out once to no avail.

I have unique domains. However when i install the dynu software on the client server for reach domain. when one checks in it updates the external ip to all unique domains. trying to figure out why this is happening.

You can assign different group names to the domains and subdomains (aliases)
in the control panel at https://www.dynu.com/ControlPanel/DDNSGroup​. Then
you can use the group in the IP update client
update the hosts that belong to the particular group.

Thank you. After creating a individual group for each domain. They seem to be updating correctly.