If you are using the same object on multiple firewalls, it must have the same name in the FMG ADOM DB. This is the Policy & Objects section of the FMG GUI. If you use one policy package for multiple fortigates, that will reference objects in the Object Configurations section.
These objects will be installed to all fortigates with the same name as in the ADOM DB. You could "Import Policy" from Device Manager to get a profile from one FortiGate and then install that to another FortiGate - FMG will delete the unused profile from the FortiGate, installing and referencing the new one instead. Generally when using a FortiManager, configuration is done in FMG and not on the FGT's.
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