Adjusting Crop of add_image_size Images After Upload

The theme I’m working with has a number of additional images sizes added by add_image_size, some of which are alternate thumbnails.

The problem comes when the crop needs adjusting, like you can do with the crop of the default thumbnail, after the photo has been uploaded into the WP media gallery.

Is there a way to crop these additional add_image_size photos after the fact? Other than re-uploading a cropped version of the original photo?

Thanks.