What’s New in FortiManager v5.0 : FortiManager v5.0 Patch Release 4 : ADOM firmware version support
 
ADOM firmware version support
ADOMs can now manage FortiGate devices running different firmware versions.
Each ADOM is associated with a specific FortiOS version, based on the lowest firmware version of all the devices that are in that ADOM. This version is selected when creating a new ADOM (see “Adding an ADOM”), and can be updated after the all of the devices within the ADOM have been updated to the latest FortiOS firmware version.
See “ADOM versions” for more information.