Have the shrubs been checked periodically thus far for watering needs? Much of Maryland has been in a drought all summer, and hydrangea have limited drought tolerance. Plus, hydrangea leaves will wither and drop after one or more frosts/freezes, since they don't really change color in autumn and are not retained because they are not evergreen. Leaves on even the healthiest hydrangeas will darken or become limp and fall in the next few weeks, if not sooner.

Soil moisture can vary from one location in a garden planting (or part of the yard) to another, so the same type of plant in different locations won't necessarily be equally hydrated, and perhaps the damaged-looking plant was drier than the one with mostly-green leaves. Similarly, minor differences in exposure to wind, sun, warmth-retaining brick or stone, etc., can impact how cold each plant actually gets on nights when it nears freezing, so one plant might be getting frosted, damaging the leaves, while the other isn't (yet). Although autumn frosts do technically cause leaf damage, per se, it's not harmful to the plant because it's not a species that keeps leaves during winter, so it's a natural process the plant is adapted to handle. Therefore, assuming the roots are still healthy, the worse-looking plant fortunately doesn't really need to be salvaged, since there's nothing wrong with it. Even if it dehydrated too much before now, watering as-needed from now on can help it not become root-damaged, but won't cause new leaves to regrow now because it's the end of the growing season, though they would regrow in spring.

The shrub that looks bedraggled isn't necessarily dead; it's probably just going dormant earlier than the other shrub. Since these types of hydrangea (Hydrangea macrophylla) bloom entirely (or primarily) on old growth, the bare stems it will retain through the winter need to not be pruned off, even if it's an eyesore. Otherwise, you may remove all of (or the early-season portion of) next year's blooms. Let any dying leaves fall off when they're ready, then they can be pulled or raked off the base of the plant and disposed of (or composted, if you prefer). Only the dried/spent flower clusters at the branch tips can be cut off, since if the stems were cut shorter instead, that would remove flower buds.

Even though the leaves are lost for autumn/winter, the root systems of the plants would benefit from occasional monitoring for watering needs (see the linked page for guidance). During a mild spell in winter, if we haven't had enough rain or snow, watering as-needed can benefit plants, particularly those that are either evergreen or which have blooms that open in spring or early summer. If any hardy plant dehydrates due to drought during dormancy, some of its dormant flower and leaf buds for the following year may be damaged or killed.

Any hydrangea leaves showing spots from minor infections can be ignored, as they are not a threat to plant health this late in the year. (Even when they turn up mid-season in a wetter year, such leaf spots are just cosmetic and unappealing, and rarely cause any serious damage to the plant.) Still, this shrub looks overly dense, so would benefit from being thinned next year, where select stems are cut down out of the clump to open-up the branching to better airflow, which also helps to reduce the severity of common leaf diseases. Our Pruning Hydrangeas page can help with that.

Miri