Some images not using WebP?

I can see in the network tab that some images on my page are loading as WebP and some are staying as PNGs (Web-Design-3-300×119.png) even in the ‘type’ section.

I’m wondering if this is because I’m using PHP to call the image in ‘large’ size. Is there a way to fix this or a way to do the same thing but still use WebP?

<?php $image_2_url = wp_get_attachment_image_src(1065, 'large'); ?>

<img alt="Web design drawn out on paper" class="banner" src="<?= $image_2_url[0] ?>">

The page I need help with: [log in to see the link]