Hydrangea wilting one branch at a time.

A few weeks ago, I noticed a single branch of my hydrangea wilting. After a while, I cut it back because I realized it wasn't going to perk up. Now another one is wilting. The rest of the bush is doing fine, except for one set of blooms that seems deformed. This bush isn't nearly as tall or as healthy as the one that's 10 feet away in the same bed. I don't know whether this one is diseased or has some sort of boring/ burrowing pest.

What really made me sad is that this was the only branch that was blooming blue. All my others are pink.

Has anyone seen this before?

Here's a longer shot of the same bush:

Mine wilt when they need water, and they perk up by the next morning. Are they in full sun, or do they get some afternoon shade?
During the hottest days, I have to water them almost daily.
I'm no expert at hydrangeas, but this is what I've noticed.

We've had torrential rains the past week, so I suspect it couldn't need water. I do wonder whether that one teeny part of the plant gets more sun than the rest. My other hydrangea is HUGE now, and is blooming like crazy. This one is obviously in the wrong part of the flower bed.

The initial symptoms of overwatering are very similar to those of underwatering, so if you've been having a ton of rain lately that's a possibility too. But it does seem weird that it's just one stem at a time, if it was over or under watering causing the wilting it would probably affect more than one branch. But if something's chewing on the base of the stems, that could cut off the water supply to that one branch but not to the rest of the plant. Can you pull back the other branches and look down all the way to the base of the wilted branch and see if you see any sort of damage (or guilty looking insects)? I would also look for signs of signficant bending, if someone/something managed to accidentally break or partially break the branch near the base, that would have the same effect. It's also possible it's gophers or voles or something chewing on the roots, but usually that'll make more of the plant wilt, so I'm suspecting damage to the individual branch.

I now think this may be physical damage from a garden critter. My evidence: Closer inspection revealed this branch had been snapped off at the base. Last night, rustling was heard in both flower beds. Flashlight investigation revealed nothing. This morning, however, a strange dropping was found near one flower bed. Of course, all this evidence is circumstantial at best, but I think it paints a plausible picture.

Well, glad you've discovered the cause. There are all sorts of critters that hang out in the garden at night, at my old house I had a family of raccoons that would make all sorts of noise out in the yard at night and I would frequently find bits of plants that they had broken off as they trampled through the garden. There are also skunks, possums, and probably others as well that are active at night.