have you tried restarting the DNS Server service on DC2.

Yes That would be my recommendation. Once you have done that you can use NSLOOKUP to verify DNS is properly returning lookups on DC2. Google NSLOOKUP to get...

Check the primary DNS zone on DC1, this is the zone that matches your FQDN of your domain. Right mouse click and on the general tab you will see...

SOunds like you only have one active DNS server in your environment. I repeat my recommendation to install DNS on DC2.

For the DHCP settings, check the scope...

You also want to ensure that the second DC has DNS installed and ensure all of your member machines have the IP for the second DC set as the secondard...