Posing Makehuman mhx in blender

I have imported a makehuman mhx, using rigify, into blender. When I pose the mouth, open it a little bit, grey dimples are appearing on both sides of the mouth, as I hope you can see in the image. Any idea how to stop this? I’ve been touching them up in photoshop, but I’d like to find a solution. Also if anyone has any tips for creating eyebrows I haven’t had much luck using hair (eyebrow hair that is), or just uv mapping them. Thanks.