How to promote stronger stems in French hydrangeas?
Occasional pruning can help create a sturdier plant, especially if its still a younger plant and the stems are having difficulty handling the weight of the blooms. However, make sure you prune at a time that won't affect its blooming. This article will help with that: https://www.gardeningknowhow.com/ornamental/shrubs/hydrangea/prune-hydrangea-bushes-hydrangea-pruning-instructions.htm