Random String Added to IMG URL's

Hi there, i’m having trouble with my images. They are not working with my lightbox theme plugin suddenly.

I noticed that the images have a random string of ?soidh2xh (characters vary per img)

For example: https://www.hardcandymusic.com/wp-content/uploads/2011/09/ladygaga-marrythenight4.jpg?5c1bf2

I have deactivated all plugins, and still can not figure out what is causing this.

Please let me know if you have any ideas. Thanks so much.