I've just noticed this too since upgrading to iTunes 12.5.1.21. I've just reported it via the iTunes Feedback page.
I've also noticed that some people have recommended turning scaling back down to 100% to fix this problem on Windows. However, I use a 1440p display and that means that all my other DPI aware programs would look wrong at this scaling level (with text and UI elements too small). The correct solution would be for the iTunes Store page to be DPI aware. Hope Apple can put this right - sooner rather than later. I've also noticed that media searches carried out within the store in iTunes don't suffer from this bug.