MBS just can't take any more.  10yr yields are still down 18bps but MBS are coping with too much supply and too much prepayment risk to do anything good anytime soon.  

UMBS 2.5s are down an eighth on the day and more than a quarter point from the morning's higher levels.  As such, don't be surprised to see a few early reprices from lenders who were already out with rates.