I have 5 lavender plants in a raised garden. They were beautiful, lush and growing well until a few days ago. I am a beginner and was very proud of how they were thriving. It seems as if they are dying from underneath up. Everything under the plant is turning black and dead. I spoke to a local nursery and they said it sounded like root rot, but couldn't tell me what to do. Is there anything I can do to save my plants? If not, is there any way I can harvest the leaves or have cuttings? Any help would be very much appreciated! THANKS! Kim