Keyboard key maintenance question

This is a cosmetic question I figured I would throw out to the fine folks on here to see if I could get any solid advice. I've had my MacBook Pro since December and over time, I have noticed the surface of the left shift key displaying a sort of sheen on it's surface that is not present on any other key. I do use this key often when using one of my apps, but I had done the same with my previous 2015 MacBook Pro and never once did it develop this sheen to it over time. I've tried several ideas such as a 50/50 water + Isopropyl alcohol to it with a soft cloth to no avail. Please see the included photo for reference.

Does anyone else have this issue or have any other ideas to remove the sheen? Thanks!