I had to strip the extra css from all youtube embeds

Whenever I embed a youtube vid onto a page in this theme, it displays with a huge empty space above the vid. (Windows 10 desktop, Chrome or Explorer browsers) You can see this at http://www.diminished5th.nz/home-page/ (a dummy page just to explore the problem) However, if I go into the properties for the block and remove the extra css classes that have been automatically added in the advanced section, ie wp-embed-aspect-16-9 wp-has-aspect-ratio then it displays just fine, with no space above it. So is there something wrong with these css classes?