issues width lightbox2, multiupload and classes


i have a huge problem on my site:
I used the modul “multiupload_imagefield_widget” for the multiupload and a Bootstrap based theme. Normaly i add the “col-md-4” class to the Only local images are allowed. field so i can display the images in three columns.
But when i change the format from “Image” to “Lightbox2” for my nodetyp in structure/nodetype/managedisplay it deletes my definied classes. Without the Lightbox it works perfectly…

i hope anyone can help me
thanks alot!
cheers dfresh

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