[Support request] Gallery Block Image Spacing CSS

Hi

I would like to increase the space between the images in my galleries by a few px to give the images some breathing room.
I input wp-block-gallery in the Additional CSS class(es) box and then added

.wp-block-gallery {
    margin-bottom: 4px !important;
    margin-right: 4px !important;
}

in the Additional CSS section.

I have no cache plugins installed yet or a CND and I cleared the browser before reloading the page and there is no change at all to the page.