Uneven watering makes the leaves dry out when the soil is dry and you end with stems with just a few or no leaves. Depending on how long your growing season is, the plant may grow new leaves now or in the Spring. And for sure, it will wait until summer temperatures moderate.
The brown leaf spots are a common fungal infection called leaf spot or Cercospora Leaf Spot. It is caused by overhead watering. There is no cure but most people handle the problem using good "clean housekeeping practices". Start by watering the soil -never the leaves- early in the mornings. Dispose of plant debris in the trash since the leaves and blooms can contain fungi. Remember this when the shrubs finally go dormant in the Fall.
You can apply fungicides in cases of a big infestation and the link below gives the names of fungicides for controlling leaf spot. I have this issue in selected shrubs planted in the ground and control it by using drip irrigation and limiting the overhead watering to the hottest periods of the summer. If I see a leaf with 1/4 to 1/3 of its surface covered by leaf spots, I will consider cutting it off and throwing it in the trash. The problem usually becomes obvious as the summer winds down and Fall starts.
Here is more information:
The brown stem spots resemble color changes that I have noticed on some of my mophead and lacecap hydrangea stems at this time of the year. I assume that they are part of the natural process of hardening in preparation for winter but, you should keep an eye for other symptoms just in case. There are certain types of root rot and bacterial infections that can produce similar symptoms; they are rare though. At this point, I do not "see" anything that would have raised a red flag for me.
You can prune dried out looking stems if they have not leafed out by mid-to-late May.