Social Media Widget causing pages to be Non Secure

This website has an SSL certificate, but many pages are showing as Not Secure because of the image files associated with Facebook, Twitter and Instagram. Using Firefox, you can get details on the media files that are preventing the page from being secure. Here’s the Facebook link: https://communityhouse.org/wp-content/plugins/social-media-widget/images/default/32/facebook.png.

I’ve been able to fix other media file issues by simply changing the code from http to https, but the plugin files are not readily available. It’s affecting a number of pages.

How can I fix this?
Tom

The page I need help with: [log in to see the link]