Reporting back! Issue resolved. Not 100% sure what the root cause was.
Updating Event Espresso seemed to be the last step that resolved the issue. Wordpress and Photon were also updated first without resolving the issue.
Now on Event Espresso Version 3.1.29.1.P and the URL comes up as
http://i2.wp.com/mysite.com/wp-content/plugins/event-espresso/images/icons/remove.gif?w=550
Notice the change in the parameter from ?resize=550%2C9999.