I found the solution by changing the query with this :
<?php
$query = new WP_Query( array(
'showposts' => 6,
'category_name' => 'une',
'post_type'=> array('post','spectacles','photos','videos')
) );
?>
<?php if($query->have_posts()) : while ($query->have_posts() ) : $query->the_post();?>