Try this code. I will added order by modified by date. Hope is work
https://codex.wordpress.org/Class_Reference/WP_Query
$args = array(
'post_type' => 'post',
'post_status' => 'publish',
'posts_per_page' => -1,
'orderby' => 'modified',
'order' => 'DESC',
'meta_key' => 'picture_upload_1'
);