You will need to use the app to control the Five’s volume. When grouped, the volume slider will affect all rooms in the group; tap the volume slider and separate controls for each room will appear. 

Alternatively, install SVC. This controls the group master volume. 

Another option is a third party remote. Some, such as the IKEA sound remote, also act on the group master volume.

Well good news. There was an update today to add voice control and now when I say Hey Sonos and give it a command to mute, lower or raise volume it controls both the beam and the five