image quality after adding data-position="fixed"

image quality after adding data-position="fixed"

My footer is a grey strip with 4 social media icon links. Looks great normally however since adding data-position="fixed" to the footer to ensure it sticks to to the bottom of the screen at all times, the image quality reduces.

See both images below, the top one being before adding the fixed code and the bottom being after. I have tested and as soon as I remove the 'fixed' code my images are perfect again. Are they somehow being stretched by the css assigned to the fixed footer code?

I tried adding even larger HQ images after adding the fixed code but same problem. It's a weird one for me?

http://www.magnetikmedia.co.uk/m/images/image_links.png