Remove space between posts

Hi, I am using show posts to show the posts in full in 2 columns. Unfortunately there seems to be a lot of space between each post vertically. I have put some horizontal lines in at the top and bottom of the posts on this page (https://perioptest.com/all/) to help show what I means.
Is there some css I can modify to reduce this? The rest of the pluging is great and works as promised.

Cheers Paul

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