Find out who last modified a Guru Card:
Navigate to Card Manager in the web app.
Select the Display Columns icon in the top right corner of Card Manager.
Select Last Modified Date and Last Modified By in the dropdown menu.
Sort the filtered results by the Last Modified Date to gather data on the Cards you need.
Now you'll see a list of who last modified a Card and what date they did this.
You can see a full revision history on a Card by opening a Card and navigating to the Details tab at the top of a Card.