Layout issue with Make Theme

I’m helping a friend to resolve some issues on her website that is using your WP theme MAKE

Before the troubles (6 months ago), the layout of the homepage was with 3 columns with images regularly disposed, with the same space between each images and between each raw. (see the link). It works on mobile but not on desktop !

Now, I can figure out to fix the margin-bottom of the raw !? I didn’t made the website, so I don’t know what the webmaster have done before…

I’ve tried to figure out how to change this issue: 
> with the theme in the widget specifications, but t doesn’t change anything !?
> with CSS code and it change it on the debug page if I use : .gallery-icon {
line-height: 5; }
but not after saving the changes on the additional CSS !?
> I’ve also try with the WP Media folder parameters but it’s always the same layout, no space at the bottom of the raw !?

It has to have a conflit somewhere, but I didn’t find it… do you have any idea how I can fix this problem ?

Many thanks in advance for your advice.

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