Ukraine, as a market mover, went from a distant memory yesterday to 'front and center' for most of today. As global financial markets weigh the prospects of civil war--chiefly the involvement of larger nations like the US and Russia--bond markets have rallied strongly and stocks have sold-off.
Treasuries, which benefit more from such flight-to-safety trading, had already broken below yesterday's low yields. MBS have now joined them in breaking yesterday's best levels, though they continue to lag overall (which is normal in these cases).
Still, the incremental improvements make positive reprices incrementally more likely. We're in a situation now where if you haven't seen a reprice yet, you almost certainly will. Fannie 4.0s are up a quarter of a point at 104-20 and Fannie 3.5s are up 10/32nds at 101-16.