Hello Richard,
I have checked your site and based on the browser's console, it seems the images are using non-relative urls: http://take.ms/pHFw7
I checked the editor that you use for creating EasyBlog posts, JCE and found that this setting is disabled: http://take.ms/kJwPi
This means that when you uploaded those images last time when your site was still under http, the 'http' protocol is included so when you switched the site to use https, those images are still in http.
Relative url do not include the 'http' protocol so when you switch the SSL in your site, the images would not affect the content security.
I would suggest you to modify the http protocol of those images in the post if you want to address those warning messages.