Can my galaxy s5 get a virus?

I think i got a virus or something that changed the resolution (graphics, i think?) on my phone. It runs a little slower, the app icons dont look 3D anymore (they look 2Dish), i went on bing and looked up the images for how the phone icons are supposed to look, even when resetted to factory, and the icons on the images dont look the same as the ones on my phone. I even resetted my phone to factory a few times and it still keeps looking different. Its upgraded to the latest upgrade. The games play fine, i.e five nights at freddys, but im just worried that the phone wont be the same again(or i cant fix it to stop running slow, ect). Can anyone please tell me whats wrong, or how to fix it?

Thanks!

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