I found them all natural..but I recognize Seohyun different in Into The New World compare now..Yuri seems natural like Yoona..but I believe all of them are natural.^_^
From this picture, my ranking is: 1) Yoona 2) Jessica 3) Tiffany 4) Sunny 5) Taeyeon 6) Yuri 7) Sooyoung 8) Hyoyeon....................Her eyebrows those days 9) Seohyun