PiHole sets every Hostname to PiHole

Hi I am running PiHole in a Docker on my Synology NAS.

Until now it worked with no problems. However I had to change my macvlan, because i created it with a fixed ip address (with the --ip-range=...). I gave the PiHole docker the new created macvlan with the same ip address and at first everything worked. However I saw that pihole now gives every client the same hostname.
I have searched a lot, but didn´t got a solution. I hope someone can help me.
Here are some screenshots of the dashboard:

Are all these different hosts all Docker instances on the NAS, including Pi-hole? if they have the same IP, that would explain why Pi-hole names them in this way, since it's naming based on IP.

No these are all clients in my network. They have all different IP and Mac addresses.