MBS have fallen to new lows for the day, down more than an eighth on the day and more than a quarter point from the morning's highs.  The losses immediately followed the end of the Fed's MBS buying for the day (getting to be a very familiar pattern), but it's worth noting that benchmark rates are moving up as well (i.e. Treasury yields have been trending higher since 11:30am).  

Some lenders could be considering negative reprices.