Wallpapers on my iPhone not good quality

It's the iPhone 5, and I have one of the background app, but it's not good picture quality. Is it my phone (it's retina display I'm pretty sure) or is it just the app?
And if an app closes out on you (glitch) is it your phone acting up or just the app? The app froze and had black on some of the picture, and then just closed out.

It's just the app, some apps have not yet been made to go with the Iphone 5 yet and since the screen is bigger on the 5 the Iphone 4 wallpapers will stretch giving you a blurry background image.

Those from iPhone-Wallpapers.com have all high resolution.

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