I have created a custom product attribute and added the code below to display them within the grouped product table.
<td data-th="<?= $block->escapeHtml(__('Breaking Strain')) ?>" class="col item">
<?= $my_attr = $this->getProduct()->getResource()->getAttributeRawValue($_item->getId(),'breakingstrain',$_item->getId()); ?>
</td>
(/public_html/vendor/magento/module-grouped-product/view/frontend/templates/product/view/type/grouped.phtml)
However not every product will use this custom attribute, so I don't want the td to be visible if there is no data set within the attribute.