Wilting Hydragea Heads

when you say recently planted that means they do need to be watered reguarly like everyday possibly twice daily especially if its warm, even if its raining

give them a good drink and keep doing it Im guessing they should soon perk up

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Whatever you do, don't trim them at this time of year - the dead flowerheads must be left on over winter for protection, and removed in April next year, together with any obviously dead wood or tips to the branches.
As Mookins says, check that you're watering thoroughly and often enough - if compost is allowed to dry out too much, any water you then add just runs straight out. If you're not sure, turn them out of their pots to check for dryness. If its not a watering problem, I'll have some questions for you!