It depends on how you setup the quiz. If you are using question groups and used the "link to bank" button, it will not automatically rescore. If you used the "find questions" option while building the quiz, then you will be able to edit the question from within the quiz and it will rescore.
If you're comfortable with excel, you can pretty quickly handle the first situation by exporting stuff from Canvas to determine who should get points, and then making an extra credit assignment that awards 1 point to just those people. I can write out the steps for this in more detail if that is an option you think would be helpful.
Here's an article about regrading quiz questions: https://community.canvaslms.com/docs/DOC-13064-4152139337
