Make space between portfolio cubes

Hi,

I wanted to make some 5px-10px space between the portfolio cubes, and I tried using this code in my child theme style:

And I did get that spacing, but the portfolio cube items got stretched by a margin that much that I lost the 3rd column (For Portfolio I use Columns Count: 3), and everything went into 2 columns.

Is there something I can do with portfolio cubes (ish-p-col) or the container (ish-p-items-container) to keep the 3 columns and spacing?

Regards,
Milosh