hydrangea leaves are turning brown/black and curling
These two plants have no blooms on them. They start out great looking then get the chewed leaf look.
Certified GKH Gardening Expert
It could be either black spot or sooty mold. Both are treatable and in most cases, not fatal to the plants. These articles will help:
(this is about black spot on roses, but it applies to all plants) https://www.gardeningknowhow.com/ornamental/flowers/roses/black-spot-roses.htm
Also, sooty mold is caused by pests, so look for them as well. Fortunately, there is an organic solution that treats this fungus (and the peststhat cause it). Treat the affected with neem oil once a week for amonth. Here is more information on neem oil: https://www.gardeningknowhow.com/plant-problems/pests/pesticides/neem-oil-uses.htm