genesis grid loop only showing one column

The following code is in home.php and works, mostly. It's not displaying a grid though. Instead it's displaying the featured image from the feature post at the top which is fine but the grid posts/images are all in a single column below the featured post. Is there something else I need to do?

?php
remove_action('genesis_loop', 'genesis_do_loop');
add_action( 'genesis_loop', 'gabbro_posts_grid_loop' );
function gabbro_posts_grid_loop() {

  if ( function_exists( 'genesis_grid_loop' ) ) {
    genesis_grid_loop( array(
      'features' = 1,
      'feature_image_size' = 1,
      'feature_image_class' = 'align none post-image',
      'feature_content_limit' = 250,
      'grid_image_size' = 'grid-image',
      'grid_image_class' = 'align none post-image',
      'grid_content_limit' = 20,
      'more' = __( 'Continue reading...', 'genesis' ),
      'posts_per_page' = 5,
    ) );
  } else {

    genesis_standard_loop();

  }

}

genesis();

functions.php is:

add_image_size('grid-image', 250, 79, TRUE);
add_image_size('featured-image', 1102, 350, TRUE);

gist for blog.html gist for style.css