The districts network has recently been switched from manual IP to DHCP. My problem is I am finding some computers inheriting the wrong IP address were do I start?

"The districts network " huh what network? how is it configured? using what OS ? and the clients are using what? please do not ask a question like this and expect a reply.

without information, there is no way to know where to start. numerous issues/things can cause DNS problems from the servers, to the clients themselves