Insert the post ID in the_field function. See the documentation.
<?php the_field($field_name, $post_id); ?>
$field_name: the name of the field to be retrieved. eg “page_content” (required)$post_id: Specific post ID where your value was entered. Defaults to current post ID (not required). This can also be options / taxonomies / users / etc
So in your case use the_field('tour_length', $item->ID) to retrieve the correct data for the specific post.