Use this plugin to regenerate the images and check the posts .
also check with inspect element to see if the images has 728×410 at the end after the regenerating .https://wordpress.org/plugins/regenerate-thumbnails/
Use this plugin to regenerate the images and check the posts .
also check with inspect element to see if the images has 728×410 at the end after the regenerating .https://wordpress.org/plugins/regenerate-thumbnails/