Lavender turning brown and drooping
Should I prune my lavender plant back I know the soil is a clay soil
The leaves look fine, it is just the blooms turning brown because they are done. Remove the spent blooms/spikes and the plant will reward you with more blooms later. As you know clay is not good for lavender but yours looks healthy now. I would do hard pruning in the winter, before the plant breaks dormancy. You can trim it anytime.