The 6.0 is at 100-29, probably not cause for concern, although a handful of lenders that priced more aggressively or "on the come," may sneak in a .125 for the worse, but with the Dow stepping back a bit in recent minutes, it's not extremely likely.  Still it will be important to keep an eye out for stocks.  If they move towards 100 pts up in the dow and similarly, if the 5 yr note gets to 3.38, it could be a forward warning of MBS weakening.