It sounds like you are using a separate port forward for each application? If so Mumble uses port: 64738 TCP AND UDP, in some routers that would be two separate entries, or others you'd be able to select tcp/udp for the port forward.
So for a separate port forward you'd need to do the following:
MUMBLE = External Port: UDP and TCP 64738 = Internal IP UDP and TCP 64738
HTTP (for rigpi UI over browser = External Port TCP XXXX (8000) = Internal IP 80
VNC = External port 5900 = INTERNAL PORT 5900 (OR A MAPPING OF YOUR CHOOSING)
However, if you move to using the PiVPN / openvpn configuratoin you would only open one port:
External port 443 (or of your choosing) UDP = Internal port 443 (or whatever port you define when isntalling PiVPN)
Then you use your phone and connect to the "openvpn" which connnext to your external IP to your RigPI then mumble, VNC, and HTTP all go over the standard ports with no router mapping.
Just my two cents and experience. I still have some external mappings for VNC so I can connect over my external IP to the RigPI vnc session without using VPN.