These buttons aren’t showing for me but if you click where you remember them being they tend to work?
They seem to be showing fine for me in Safari on iOS 12.1.2.
Weird. Same problem on iPhone 6 and iPhone Xs, admittedly with the same user profile transferred from one to the other though.
But there isn't anything to fix. I've just looked again and the buttons are showing fine for me in Safari on iOS. Have you tried clearing your browser cache? Do you have any add-ons/extensions that could be blocking the pictures? Actually, does Safari have extensions? I try to use my iPhone as little as possible.
Also, install another browser like Chrome and let us know if the pictures appear there or not.