Built lights cause white materials to turn yellow (Blender FBX)

I hope somebody can help me, because I’m ripping my hair out here. I use Blender to make models, mark seams and unwrap the UVs, then export as an FBX. I import the FBX into UE4, and throw on a white material. All pretty standard stuff. However, when I build the lights (the scene below has a skylight, and a source, both stationary) I get a cigarette stained looking model, and I have no idea why. When compared next to the same room created from UE4 cubes, it is very easy to see just how off the white material on a Blender model is (see picture). The left room is the Blender model, the right is the room made of UE4 cubes. Does anybody know why?