Is your hydrangea droopy? Are the flower heads kissing the ground? I will tell you this… The majority of the time it isn’t about the lack of water and most likely you are over watering thinking it will help perk up those lovely hydrangea heads. What is really going on is the fact that the hydrangea blossoms are too heavy for the young pliable stems of your plant. Over time your hydrangea will age (as we all do) and become a stronger version of our younger self- able to carry heavy loads under added stress. What I am trying to say in the garden world- the stems over time will become woody and stronger, allowing the stems to hold up the heavy flower heads. So, give the plant some time to mature and grow.
In the duration, you could always stake up a few of the stems to make the plant more presentable.