Blog image not aligning to centre on mobile

Image has a white border on iPhone X, can I at least align the image to the centre or maybe enlarge the image so it doesnt have the white border!

Site link is :

Hello there,

Check if your mobile web browser’s version is the latest. Or try adding this CSS code to Appearance > Customize > Additional CSS from dashboard.

    @media only screen and (max-width: 500px) {

      .blog-loop .post-thumbnail,
      .blog-loop .post-thumbnail img {
        display: block;
        width: 100%;

and see if it helps.