Authentication Problem

When the network was originally configured by a consultant, my users were Authenticating to DC1 which is our Bridgehead server Domain Controller.

Somehow that changed, my users are now authenticating to my DC2 (secondary domain controller (not a bridgehead).

Also, when running Users and Computers, it is pointing to my DC2 when it used to point to my DC1 (the way it should be).

How do I get them back to authentication on DC1?
There arent any communications issues.
This is a Win2K PureAD network.