Footer images not aligning/stacking correctly on smart phone/tablet

Hi,

I am using the McKinley WP template: https://sdcs.cgwebsolutions.co.uk and have added an widget to the footer to display images.

The images in the footer display okay on a desktop computer, however when viewing them on a smart phone or tablet they do not stack correctly and overlap each other.

I have attempted to identify the problem by tweaking the CSS, however this has not worked. Can you please advise how this can be fixed?

Thanks!