You as the organizer can edit a judge's scores or comments while an event is live or after an event. Your changes are permanent, so be careful in making edits!

On the Judges tab, click on the name of the judge you want to edit or enter scores for. Then click "Share Ballot" and then "View Ballot in New Tab".

This will open the judge's unique ballot in a new tab. You are now acting as that judge and can enter/edit scores and comments. When you are finished, you can close the tab.