Apparently the records have been stored with a trailing
. in the backend, when they should have been stored without. If you're using PowerAdmin as a frontend for PowerDNS you can simply correct this in the web UI. Open the zone in PowerAdmin and then click Commit changes on all pages containing a record that the check complained about (without changing anything). That should update the records in the format PowerDNS expects.
If you don't have PowerAdmin you need to remove the trailing dots in the backend. If you're using MySQL as the backend that would be something like
UPDATE records SET content = trim(trailing '.' from content) WHERE content LIKE '%.';