Hello and welcome to the site. Considering your location and the season it may be nothing more than a deciduous shrub losing its leaves. Do you know the species? There is not really much you can do now except wait until spring and see what happens. If you have not already done so water them in well before it gets too cold and then after the ground gets thoroughly chilled mulch them in well.
If you get curious, prune a tip from one of the branches and look for green, living tissue. Don't get too discouraged if you do not see any at the tips, snip back a little farther. This is just a test and not a "treatment" so don't go too wild. You can also look for next years buds and see if they seem viable or dried out.
Time will tell and the only thing you can really do now is wait.