Try this. Open up a preview of your problematic lesson in chrome (I know, it’ll be blurry). Copy the localhost url in the address bar (probably http://localhost:3750/page_1.html). At the top right of the screen you will see your name or a little round icon that indicates you logged into chrome. Click this icon and select Guest. Paste in the URL and hit enter. Is it still blurry?
If that fixed the problem then you probably need to delete your user profile and create a new one.
By the way, this has been an issue with chrome since the removed direct write font rendering.