I agree with what the others said, it is a combination of slight fat shifts and your brows are certainly looking more prominent. It is funny because I was having these same thoughts looking at comparison photos the other day. I got a couple at very similar angles to each other but still couldn't tell exactly what had changed, even though I knew something had because I somehow look older.
It's interesting how hard it is to have an objective opinion on one's own features, isn't it?