Classes are all duplicated in front-end calendar, but not back-end

I’m not quite sure when this happened — but even though all the classes from my earlier version of the plugin imported properly into the new version, for some reason, they’re all duplicated on the front-end calendar page.

Here’s a temporary URL to the page that’s having the problem:

http://temporaryurl.scripteen.com/i3

https://wordpress.org/plugins/weekly-class-schedule/