You can see an option in WHM to add additional nameservers. You can give only the nameserver name, but not the IP. Most of the time it will be taking some wrong IPs by its own.
To overcome this problem, you will have to edit “/etc/nameserverips” file from backend.
/etc/nameserverips should look like this:
If you want to add one more nameserver ns4.your-dns.com, you can just insert it instead of 0.