Okay so I don't think this is an alpha problem, I think it's actually a model problem. This is what it looks like after I applied my SSS materials (without the eyebrow texture, that actually also gives a strange effect tho). I'm not sure if I messed up somewhere or if it's a blender problem, but I do know that removing doubles didn't work (it did work for the other parts of the face however) and it's not a shading issue.
https://imgur.com/BGCSNgl
https://imgur.com/BGCSNgl