Your title said unique touch event for instances, so you would need a unique identifier for each instance to determine what unique event to run. You can set an instance variable when creating objects via events as well no problem.
If you want a generic event for flipping the card, then a simple on touched object would suffice - only the touched instance would be picked, and only that instance would flip.
I don't know why your previous event with for each doesn't work, as I have no idea why you would want to use for each in this situation to begin with, since for each doesn't really have anything to do with what I understand your question to be.