The more I examine my screen the more I think the viewing angle is causing most if not all of the off-white/yellow I am seeing at the bottom. I downloaded a colorimeter app (free app called "Colorometer") to my iPhone and measured my screen, and it measured no difference from top top bottom.
I've used this app too but got wildly different readings from top to bottom. Even measuring the same place gives me different readings. Not sure if the app is just that inaccurate or if I'm somehow using it incorrectly.