This plant is in its original pot. The edge of the leaves are turning brown and the flowers are no longer a bright pink but a very dull pink.
Certified GKH Gardening Expert
Typically, in hydrangea, this is caused by a watering issue, especially in containers. Hydrangeas need to be kept unifromaly moist, but not soggy. It is a good idea to check the soil with your finger and water if it feels dry to the touch about an inch or so. If it's still moist, do not water. You can remove the browning leaves and they should regrow once the plant recovers.
Since it is still in orginal pot and depending on how long it's been there, it may need to be repotted into a larger container (up another 1-2 pot sizes) or transplanted outdoors.