Why does the mobile version of my website have black blocks in the tiles?

The website is fine on widescreen view. However, on mobile devices, some of the tiles have black blocks at the bottom of them. Older pages seem to be fine, but ones that I have edited recently both seem to suffer with the same issue. I've tried resizing the image/text, and nothing seems to get rid of the black block. Can anyone help me get the whole tile to have the same colour background please?

Thank you Creedon! That worked straight away!