Some stuff...

// Don't use multiple loops here. Loop through all your posts once, and store each post into an array depending on which tier it falls into. E.g.

$tiers = array(
  'platinum' => array(),
  'gold' => array(),
  'silver' => array(),
  'bronze' => array()
);


//Afterwards, the array should be populated with posts. Loop through the array and handle it accordingly.

foreach ( $tiers as $level => $posts ) {
  foreach ( $posts as $post ) {
    // output each post
    // do some fancy output using $level if needed
  }
}