I think she revealed it during the music bank performance... Saying that her voice is not in good condition so she can't give the best performance ;'(

Seo Goddess please feel better, and you guys still did an amazing job..fighting to all snsd members.

ahh thats why her voice is a little weird
i was really worried to her

@samarkatloi she is??? ohhh my poor baby...
but she still rocked the stage with the twinkle twinkling hehe!

Actually I'm really nervous for Seohyun as she sang... cuz as we all know, she's sick and her voice is not in good condition.

Waahh... I hope she's feeling better any time soon T_T