.custom-gallery.wp-block-gallery {
    margin-inline: 0;
    display: flex;
    flex-wrap: wrap;
    --wp--style--unstable-gallery-gap: var( --wp--style--gallery-gap-default, var( --gallery-block--gutter-size, var( --wp--style--block-gap, 0.5em ) ) );
    gap: var( --wp--style--gallery-gap-default, var( --gallery-block--gutter-size, var( --wp--style--block-gap, 0.5em ) ) );
}

.custom-gallery.wp-block-gallery img {
    flex-grow: 0 !important;
  }