I'm curious about this as well. Do you have to "resubmit" your ads to google or pause/unpause them for google to notice your updated landing page? Or can QS change without any updates on your site?
Everyday they'll decrease until you hit a pretty high QS. Just make sure you keep your adgroups tight with few KWs and run 2 ads at a time. Replace the losing ad after you get enough data. Keep at it brah.