MBS are only down 2 ticks (.06) on the day, but lenders who repriced near the highest levels of the day are now seeing 6 ticks (.19) of weakness.  That's enough for many of those lenders to consider pulling pricing back a bit. 

10yr yields are still off the morning highs, but up 2.3bps at 4.095.

Nothing specific driving the weakness... just a drifty correction after the initial rally.