Sashabel
Josianne - your lavender would not have liked the new compost as it would have been far too rich for it. Lavender thrives in poor soil, so don't feed it or give it new compost. Mine is planted in a low wall at the front of my house and the soil must be dreadful for any other plant, but the lavender love it. I never water it either. Less is more with lavender.
I agree, they need poor soil. When I moved it here I inherited a raised bed/planter containing a rose and lavender round the edges. It's been hard to feed the rose without feeding the lavender. I sprinkled some granular feed just around the rose and didn't use my usual feed which I water in.
My lavender floweredearly and I cut it back a few weeks ago, but it still looks dried up and tatty. I'm probably going to replace the plants with a smaller variety.