Ok. In order to have the master as the DHCP server, you will need to change the DHCP helper address on the router where the gateway resides. You will need that to point to the master controller, after you have configured your DHCP pool for that VLAN. Or if the master has an IP address on that Guest VLAN, you can just remove the helper address from the router, as devices will ARP across the VLAN for a DHCP response, and the master, running as a DHCP server, will respond.