ACF field not appearing correctly in loop

Question

There is a loop in my theme that displays posts with the following information: a title, some text, and a price. I have added a custom field to this post type using ACF. The field ID is tour_length. I add the custom field value to the loop using <?php the_field('tour_length'); ?> however when the posts display on the front end it only displays the value for the first item and repeats it for every subsequent item.

    {foreach $posts as $item}
    {first}<ul class="items">{/first}
        <li class="item clear{ifset $item->packageClass} {$item->packageClass}{/ifset}{ifset $item->optionsDir['featured']} featured{/ifset}">
            {if $item->thumbnailDir}
            <div class="thumbnail">
                <a href="{!$item->link}"><img src="{thumbnailResize $item->thumbnailDir, w => 155, h => 115}" alt="{__ 'Item thumbnail'}"></a>
            </div>
            {/if}
            <div class="description">
                <div class="info">

                    {var $lp = getTourPrice($item->ID)}
                    {if $lp}<div class="item-price"><span><span><span class="from">From</span>{$lp}</span></span></div>{/if}

                    // HERE IS WHERE I'VE ADDED MY CUSTOM FIELD
                    <div class="item-length"><span><?php the_field('tour_length'); ?><span class="days">Days</span></span></div> 


                </div>
                <div class="desc-head">
                    <h3><a href="{!$item->link}">{$item->post_title}</a></h3>



                </div>
                <div class="desc-text">
                {if shortcode_exists( 'loop' )}
                    {doShortcode "[loop id=".$item->ID."]"}
                {/if}
                {!$item->excerptDir}
                </div>
                <a href="{!$item->link}" class="trip-order enquire-btn read-more">Learn More</a>
            </div>  
            <!-- tour offers -->
            {ifset $GLOBALS['findedOffers'][$item->ID]}
                {if count($GLOBALS['findedOffers'][$item->ID]) > 0}
                <table class="item-offers">
                    {foreach $GLOBALS['findedOffers'][$item->ID] as $offer}
                    <tr class="offer">
                        <td class="offer-title"><a href="{add_query_arg(array('offer' => $offer->ID),$item->link)}">{$offer->post_title}</a></td>
                        <td class="offer-date">{$offer->from} - {$offer->to}</td>
                        <td class="offer-price">{$offer->price}</td>
                    </tr>
                    {/foreach}
                </table>
                {/if}
            {/ifset}
        </li>
    {last}</ul>{/last}
    {/foreach}

Can someone point me in the right direction as to why that's happening?

EDIT: Implementing the solution as pointed out by Fleuv solved the issue for posts being displayed in a search. However posts being displayed in the category still show the problem. Here is the category loop:

 {foreach $posts as $item}

    {first}<ul class="items">{/first}

        <li class="item clear{ifset $item->packageClass} {$item->packageClass}{/ifset}{ifset $item->optionsDir['featured']} featured{/ifset}">

            {if $item->thumbnailDir}

            <div class="thumbnail">

                <a href="{!$item->link}"><img src="{thumbnailResize $item->thumbnailDir, w => 155, h => 115}" alt="{__ 'Item thumbnail'}"></a>

            </div>

            {/if}

            <div class="description">

                <div class="info">

                    {var $lp = getTourPrice($item->id)}

                    {if $lp}<div class="item-price"><span><span><span class="from">From</span>{$lp}</span></span></div>{/if}

                    // MY CUSTOM FIELD 
                    <div class="item-length"><span><?php the_field('tour_length', $item->ID); ?><span class="days">Days</span></span></div> 

                </div>

                <div class="desc-head">

                    <h3><a href="{!$item->link}">{$item->title}</a></h3>

                </div>

                <div class="desc-text">

                {if shortcode_exists( 'loop' )}

                        {doShortcode "[loop id=".$item->id."]"}

                {/if}

                {!$item->excerpt}

                </div>

                <a href="{!$item->link}" class="trip-order enquire-btn read-more">Learn More</a>

            </div>  

        </li>

    {last}</ul>{/last}

    {/foreach}

Answer 1

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.