I have a feeling that ERNS, NITE and SCHB are short some. This is all speculation so take it as such. The three of them hit the ask and walked the price down pretty quickly on fairly low volume. When challanged, they fled. ERNS never leaves without selling a good amount. I would guess that they want to bring the price down as low as it can go and pick up some shares on the way down - all while not having to sell too many shares at the ask.