For Juniper Networks EX/QFX Series Switches that are managed by Juniper Mist, the message "IP address x.x.x.x out of scope defined under subnet field for Network (network test) might be shown in a yellow banner at the top of the switch view page. 

Mist UI shows a warning in switches view: IP address x.x.x.x out of scope defined under subnet field for Network (network name).

Example:

The warning alerts shows up when you configure a static IP address in the "IP CONFIGURATION" for the IRBs, and at the same time a subnet configured for the VLANs.

As the warning mentions, the static configuration for the IRBs is outside of the subnet configured in the VLAN.

To fix this you can delete the subnet used in the VLAN or configure the correct subnet.