Hi Marcel,
For the 4.3 DC version, since 4.3.3, the storage format was changed to V5.
Till that version, the storage format for 4.3 DCs was V4.
Since your SDs were created before 4.3.3, their storage format should be V4.
In order to upgrade this format, you can try to detach those storage domains and attach them to a DC which its version is V5.
(On the UI: Go to the relevant SD -> Data Center tab -> maintenance and then Detach).
You should get a confirmation window that asks you to confirm the storage format's upgrade.