Custom CSS – posts not aligned

I hope somebody can help me to solve this issue.

I have a page with 4 posts, which should be displayed in a 2×2 grid. However the second row starts wrong and it is now displayed in 3×2 grid.
In English language on iPad mini in portrait mode it is displayed correctly (but I had to change the width of the full content to 83%) in landscape the four posts are not aligned properly.
In Korean, both in portrait as in landscape mode it is not correctly displayed.

http://sinheeyoga.com/workshops/
http://sinheeyoga.com/ko/workshops_/

I cannot find the correct elements to adjust,
Hope somebody can give me some direction.
Thanks in advance.

The page I need help with: [log in to see the link]