Gray Block next to the sidebar in single post view

Hi here, love the theme except for 1 wrinkle;

The images in gallery view in single post view automatically “wraps” the end image to the next line regardless of available space. This causes the thumbnail images in gallery view to leave particularly unsightly gaps as an image is wrapped down to the next line.

I have tried to remove the date and the dynamic side bar but that doesn’t affect this problem.