This plugin is loading its CSS using the WP_PLUGIN_URL constant instead of the plugin_dir_url() function, so it triggers insecure content warnings on SSL pages. It's also loading an image (pixel.gif) using WP_PLUGIN_URL. I looked at providing a "fix" (hack) for your plugin with my SSL Insecure Content Fixer but I can't because of the image being in the content generation (I don't/won't filter the content, for performance reasons; WordPress HTTPS does that job).
Fixing this in your plugin is easy though:
* use the wp_enqueue_scripts action to enqueue your CSS, instead of printing it from wp_head action
* use plugin_dir_url() to get your plugin dir, instead of WP_PLUGIN_URL, so that it handles the transition to SSL (HTTPS)
* you could also use wp_localize_script() instead of the script block in your WtiLikePostAddHeaderLinks() function, and change your scripts to access blog_url through your namespace (see link)