I use ddclient to keep my dns records updated. I seem to have found a little bug on your side when you try to update more than one alias from the same client.

DDClient seems to pack up all the alias on the same request to your servers, once you receive the request, if the last alias sent by ddclient happens to have the ip up to date your api responds with "nochg" and does not update the rest of the alias.

Since ddclient assumes then that all the alias have been updated, it caches the status of all the alias as updated with the current public ip address and does not attempt to further update any of the alias.