In the settings for the VPN on the MX84, under the section VPN settings/Local networks, are the 192.168.1.0 and 192.168.2.0 networks listed?
I've just setup something similar but to a ASA 5525 and only with 1 subnet. I'd expect any other subnets to therefore appear under the above VPN settings/local networks section and give you the option to Use VPN or not.
rgds
Gary