Three column grid page sela

Hi, used the code in this page to turn the grid page from 2 to 3 columns.
https://www.ads-software.com/support/topic/making-grid-into-three-columns?replies=4

It worked until I had 6 images, then the grid page went crazy and in some lines it appears only 1 image.
You can see my blog page here https://supermamiblog.com/b/per-ingrediente/

I also removed the part that Siobhan Bamber suggested me, from my custom CSS, but nothing changed.

Any suggestions?
I will have a lot of lines, so it is important that the page will look good!
Thanks!