Some thumbnails don't show up

Hello,

I’ve noticed the thumbnails of my recent posts don’t show up, instead there is a white image/blank image.

Also, the pluggin is against the post date below. I would like to have a small space, at least a line, between the pluggin and the date.

Thanks for your help!

http://ww.wp.xz.cn/plugins/related-posts-thumbnails/