I have two images for a website both created in Graphic Converter. They are both PNGs 720 x 405px, made exactly the same way from four screenshots from videos reduced to 360 x 203px. The code on the website, as confirmed by View → Developer → View Source, is identical. And yet if I make the browser window wider, one of them enlarges, like all the other images on the website, yet the second does not; it remains at a constant size making the page unbalanced.
Does anyone here have any idea why this might be happening? If you want to see for yourselves, it is the homepage of https://www.talkingoffood.com/ the images accompanying "Have you watched…" and "New in Movie Clips".
Many thanks.