This is probably a really hacky way to get it to work, but here’s what I did.
Go and edit the file at wp-content/plugins/easy-columns/easy-columns.php
At line 270 (in mine anyway) there is a section that starts
<!– Begin Easy Columns 1.0 by Pat Friedl http://www.affiliatetechhelp.com –>
The next line should be href=”<?php echo $this->plugin_url; ?>/css/wp-ez-columns.css?<?php echo time();?>”.
Change it to the exact URL with HTTPS of your easy-columns css file and escape the slashes. For most sites it should change to:
href=”https:\/\/YOUR_DOMAIN.com/wp-content/plugins/easy-columns/css/wp-ez-columns.css<?php echo time();?>”
Hope this helps!