Social icons display blank on hover

I think I broke my CSS and can't find the problem. I'm hoping someone here will have the answer. I am updating the child CSS, not the original. The social icons display as intended in the footer (color always), but not in the header. There the icons display in color until I move my cursor over the image, then it disappears entirely. Can't figure out what the problem is. Please help. www.sevenportions.com