I am making this test after reading: Topic: Big white space above youtube video since last update | WordPress.org. Below will be a YouTube video block.
This is the next paragraph after the video. With no caption looks like I need to add some bottom padding/margin on the front-end.
On further examination, the reason I don’t see the issue is due to the plugins I use and my Twenty Twelve theme which hasn’t been Gutenbergized yet. Many of the following CSS classes simply aren’t defined on the front-end:
<iframe src="https://www.youtube.com/embed/UQyEcspdYfY?feature=oembed" allow="autoplay; encrypted-media" allowfullscreen="" width="625" height="352" frameborder="0">
Currently, there is a WordPress/Gutenberg GitHub Issue concerning this.