You manage to work this by using the following code to your group.phtml
<?php
/**
* Copyright © Magento, Inc. All rights reserved.
* See COPYING.txt for license details.
*/
// @codingStandardsIgnoreFile
/**
* Grouped product data template
*
* @var $block \Magento\Catalog\Block\Product\View\BaseImage
* @var $block \Magento\GroupedProduct\Block\Product\View\Type\Grouped
*/
?>
<?php $block->setPreconfiguredValue(); ?>
<?php $_product = $block->getProduct(); ?>
<?php $_associatedProducts = $block->getAssociatedProducts(); ?>
<?php $_hasAssociatedProducts = count($_associatedProducts) > 0; ?>
<div class="table-wrapper grouped">
<table class="table data grouped" id="super-product-table">
<caption class="table-caption"><?= /* @escapeNotVerified */ __('Grouped product items') ?></caption>
<?php if ($_hasAssociatedProducts): ?>
<?php $showStrapwidthTxt = 0; // Flag set to 0 ?>
<?php $showStraplengthTxt = 0; // Flag set to 0 ?>
<?php $showBreakingstrainTxt = 0; // Flag set to 0 ?>
<?php $showSystemstrengthTxt = 0; // Flag set to 0 ?>
<?php foreach ($_associatedProducts as $_item): ?>
<?php if($this->getProduct()->getResource()->getAttributeRawValue($_item->getId(),'strapwidth',$_item->getId())){ $showStrapwidthTxt = 1; } ?>
<?php if($this->getProduct()->getResource()->getAttributeRawValue($_item->getId(),'straplength',$_item->getId())){ $showStraplengthTxt = 1; } ?>
<?php if($this->getProduct()->getResource()->getAttributeRawValue($_item->getId(),'breakingstrain',$_item->getId())){ $showBreakingstrainTxt = 1; } ?>
<?php if($this->getProduct()->getResource()->getAttributeRawValue($_item->getId(),'systemstrength',$_item->getId())){ $showSystemstrengthTxt = 1; } ?>
<?php endforeach; ?>
<?php foreach ($_associatedProducts as $_item): ?>
<tbody>
<tr>
<td data-th="<?= $block->escapeHtml(__('Product Name')) ?>" class="col item">
<strong class="product-item-name"><?= $block->escapeHtml($_item->getName()) ?></strong>
</td>
<?php if($showStrapwidthTxt): ?>
<td data-th="<?= $block->escapeHtml(__('Strap Width')) ?>" class="col item">
<?php if($my_attr = $this->getProduct()->getResource()->getAttributeRawValue($_item->getId(),'strapwidth',$_item->getId())): ?>
<?= $my_attr; ?>
<?php endif; ?>
</td>
<?php endif; ?>
<?php if($showStraplengthTxt): ?>
<td data-th="<?= $block->escapeHtml(__('Strap Length')) ?>" class="col item">
<?php if($my_attr = $this->getProduct()->getResource()->getAttributeRawValue($_item->getId(),'straplength',$_item->getId())): ?>
<?= $my_attr; ?>
<?php endif; ?>
</td>
<?php endif; ?>
<?php if($showBreakingstrainTxt): ?>
<td data-th="<?= $block->escapeHtml(__('Breaking Strain')) ?>" class="col item">
<?php if($my_attr = $this->getProduct()->getResource()->getAttributeRawValue($_item->getId(),'breakingstrain',$_item->getId())): ?>
<?= $my_attr; ?>
<?php endif; ?>
</td>
<?php endif; ?>
<?php if($showSystemstrengthTxt): ?>
<td data-th="<?= $block->escapeHtml(__('System Strength')) ?>" class="col item">
<?php if($my_attr = $this->getProduct()->getResource()->getAttributeRawValue($_item->getId(),'systemstrength',$_item->getId())): ?>
<?= $my_attr; ?>
<?php endif; ?>
</td>
<?php endif; ?>
<td data-th="<?= $block->escapeHtml(__('Price')) ?>" class="col item">
<?php if ($block->getCanShowProductPrice($_product)): ?>
<?php if ($block->getCanShowProductPrice($_item)): ?>
<?= /* @escapeNotVerified */ $block->getProductPrice($_item) ?>
<?php endif; ?>
<?php endif; ?>
</td>
<td data-th="<?= $block->escapeHtml(__('Multiple Discount')) ?>" class="col item">
<?php if ($block->getCanShowProductPrice($_product)
&& $block->getCanShowProductPrice($_item)
&& trim($block->getProductPriceHtml(
$_item,
\Magento\Catalog\Pricing\Price\TierPrice::PRICE_CODE
))): ?>
<?= $block->getProductPriceHtml(
$_item,
\Magento\Catalog\Pricing\Price\TierPrice::PRICE_CODE
) ?>
<?php endif; ?>
</td>
<?php if ($_product->isSaleable()): ?>
<td data-th="<?= $block->escapeHtml(__('Qty')) ?>" class="col qty">
<?php if ($_item->isSaleable()) : ?>
<div class="control qty">
<input type="number"
name="super_group[<?= /* @escapeNotVerified */ $_item->getId() ?>]"
data-selector="super_group[<?= /* @escapeNotVerified */ $_item->getId() ?>]"
value="<?= /* @escapeNotVerified */ $_item->getQty() * 1 ?>"
title="<?= /* @escapeNotVerified */ __('Qty') ?>"
class="input-text qty"
data-validate="{'validate-grouped-qty':'#super-product-table'}"
data-errors-message-box="#validation-message-box"/>
</div>
<?php else: ?>
<div class="stock unavailable" title="<?= /* @escapeNotVerified */ __('Availability') ?>">
<span><?= /* @escapeNotVerified */ __('Out of stock') ?></span>
</div>
<?php endif; ?>
</td>
<?php endif; ?>
</tr>
</tbody>
<?php endforeach; ?>
<?php else: ?>
<tbody>
<tr>
<td class="unavailable"
colspan="<?php if ($_product->isSaleable()): ?>4<?php else : ?>3<?php endif; ?>">
<?= /* @escapeNotVerified */ __('No options of this product are available.') ?>
</td>
</tr>
</tbody>
<?php endif; ?>
<?php //Copied thead from top to bottom ?>
<thead>
<tr>
<th class="col item" scope="col"><?= /* @escapeNotVerified */ __('Product Code') ?></th>
<?php if($showStrapwidthTxt): ?>
<th class="col length" scope="col"><?= /* @escapeNotVerified */ __('Strap Width') ?></th>
<?php endif; ?>
<?php if($showStraplengthTxt): ?>
<th class="col length" scope="col"><?= /* @escapeNotVerified */ __('Strap Length') ?></th>
<?php endif; ?>
<?php if($showBreakingstrainTxt): ?>
<th class="col length" scope="col"><?= /* @escapeNotVerified */ __('Breaking Strain') ?></th>
<?php endif; ?>
<?php if($showSystemstrengthTxt): ?>
<th class="col length" scope="col"><?= /* @escapeNotVerified */ __('System Strength') ?></th>
<?php endif; ?>
<th class="col indi" scope="col"><?= /* @escapeNotVerified */ __('Individual Price') ?></th>
<th class="col multi" scope="col"><?= /* @escapeNotVerified */ __('Multiple Discount') ?></th>
<?php if ($_product->isSaleable()): ?>
<th class="col qty" scope="col"><?= /* @escapeNotVerified */ __('Qty') ?></th>
<?php endif; ?>
</tr>
</thead>
</table>
</div>
<div id="validation-message-box"></div>
