Slow Site After Purchasing Addons

The site was functioning perfectly, then after purchasing the Messaging and Multi-Class addons, the site takes 5-8 seconds to load each page. Disabling one cuts this in half, disabling both and the site is back to loading instantly. I saw there was someone with this same issue a year ago marked ‘Resolved’ but there was not reply with a resolution. Separately, the notice “To enable add-on functionalities, please add your license key in WPSchoolPress General Settings” never goes away (there’s 2 of them, one for each add-on), and reappears on every page load.