Video box problem on iOS mobile

Hello!

If you see a video post (embedded vimeo,youtube) in Ryu theme on iOS device (safari..),
the embedded video ‘black’ box appears very long vertically in the post.

See this page in iOS device Safari,
https://ryudemo.wordpress.com/category/videos/

I don’t know how to fix this issue? Is there a solution?

Best,

Jun