DNS with third server wont sync

[scube]

We are running three Servers, first is 8.1, second is 7.5.4 and the newest, the third, is 8.0.

The DNS is dns1.artack.ch and dns2.artack.ch which are the first and second server.

Now I can't get work that the third server is sync the DNS zones to the first and second server,
does anyone have a hint for me?

thanks