Wp_query with multiple custom fields returning 0 results

In wordpess 4.1, I have the following WP_Query:

$products = new WP_Query( array(
        'post_type'      => 'ys_product',
        'orderby'        => array( 'date' ),
        'order'          => 'DESC',
        'posts_per_page' => 8,
        'meta_query'     => array(
            'relation' => 'AND',
            array(
                'key'   => 'ys_product_status',
                'value' => 'ok'
            ),
            array (
                'key'   => 'ys_product_start',
                'value' => date('Ymd'),
                'compare' => '>='
            ),
            array (
                'key'   => 'ys_product_end',
                'value' => date('Ymd'),
                'compare' => '<='
            )
        )
    ) );

      

        
        
        
      

    

And on my DB I have two items with post_type 'ys_product' and with post_meta like this:

Paragraph 1

• meta_key ys_product_status = 'ok'
• meta_key ys_product_start = '20141101'
• meta_key ys_product_end = '20141230'

Point 2

• meta_key ys_product_status = 'ok'
• meta_key ys_product_start = '20141101'
• meta_key ys_product_end = '20150131'

The result of the date ('Ymd') today is "20141226", which is clearly visible between these boundaries.

But if I'm only looking for filtering by 'ys_product_status' == 'ok'; I get my two items. But when I add the other two meta, they won't return any results at all.

Content of the $ products-> request:

SELECT SQL_CALC_FOUND_ROWS  ysls_posts.ID
 FROM ysls_posts 
 INNER JOIN ysls_postmeta ON ( ysls_posts.ID = ysls_postmeta.post_id )
 INNER JOIN ysls_postmeta AS mt1 ON ( ysls_posts.ID = mt1.post_id )
 INNER JOIN ysls_postmeta AS mt2 ON ( ysls_posts.ID = mt2.post_id )
WHERE 1=1
 AND ysls_posts.post_type = 'ys_product'
 AND (ysls_posts.post_status = 'publish' OR ysls_posts.post_status = 'private')
 AND ( 
  ( ysls_postmeta.meta_key = 'ys_product_status' AND CAST(ysls_postmeta.meta_value AS CHAR) = 'ok'  ) 
   AND 
  ( mt1.meta_key = 'ys_product_start' AND CAST(mt1.meta_value AS CHAR) >= '20141226' ) 
   AND 
  ( mt2.meta_key = 'ys_product_end' AND CAST(mt2.meta_value AS CHAR) <= '20141226' )
 ) GROUP BY ysls_posts.ID  LIMIT 0, 8

      

        
        
        
      

    

The post_meta content for the two targeted posts:

What am I doing wrong?