You could use the Broadcast All option in Send Event with an event that only those copies are listening for.
Or you could use the GameObject option with Send To Children checked, and parent your copies to a common parent.
The next update will have native support for arrays which will let you fill an array with the target objects and send an event to each target. You could build a loop manually now, but it would be more work If one of the methods above works for you I'd go with that...
There may also be custom actions that do other things, like send an event to all GameObjects with a given Tag... I seem to remember seeing something like that...