Hmmm, since they aren't teething yet (are there gums even the slightest bit swollen by chance?), it might just be another growth spurt. Do they seem like they'd be wanting to eat a bottle when they're up or are they just fussing to fuss?
This was about the time my DDs had crazy hours all of the sudden too. There were times I let them CIO (more painful for me than them) and other nights I'd surrender and let them go in the swing and then transition them back to the crib or let them cuddle me then eventually go in their own cribs. Sometimes the trick for us was to just give a small (couple oz.) bottle and then back to bed.
GL and hope they're STTN again ASAP!