@media (min-width: 600px){
    .wp-block-gallery.has-nested-images.columns-3 figure.wp-block-image:not(#individual-image){
        width: 30%;
    }

    .wp-block-gallery.has-nested-images.columns-default figure.wp-block-image:not(#individual-image){
       width: 30%;
   }
}