Look at the base to see if it was damaged or critters chewed it.

tj

I don't see any evidence of critters eating the limb. It's really odd. Thanks

At my place once they reach a certain age the older branches die off as the new sprouts gain size.

I would give it a hard pruning after it finishes flowering. I'd take any shriveled branches off at the ground. I would use a separate tool on the shriveled branch and clean it well with alcohol after ward. And it's early in the season, I'd think you could add some good compost around the base, staying 4-6" away from the trunk. Soak it good and cover that with mulch and then just keep it watered well the rest of the season and see how it does. I am no expert, but that is what I'd do.

If it's the same limb every year, prune off that limb and only that limb. Disinfect the pruner afterwards. And prune it off in late winter/early spring, not in the fall.

Thanks for the replies everyone. I'll prune them to the base and add compost.

Not necessary to prune the whole bush to the ground, but any dead branches and you could trim the rest of the shrub to shape, right after you've had enough of the blooms. and as Laceyvail suggested disinfecting your pruners afterwards. Which I am sure you already know... Good luck! :-)