Dave, thanks so much for asking the most insightful questions. Ive tried to grow lavender here in Alabama and just couldn't understand why the plants died. I did grow wonderful lavender beds with roses in California. Now I know exactly why: Santa Barbara has dry weather alkaline (gumbo) soil with a mean mean temperature of 70 degrees F year round. Central Alabama has hot humid weather, and acid soil, summers are wet and hot--100 degrees plus over the last three months.
The tip on anti-fungal drench was right on the money. After day after day of RAIN for months now (while the rest of the country is having drought) I think anti-fungal drench is just what I need to save some of my rotting plants.
And maybe I could try to build a raised bed with alkaline soil, with some sort of shelter to keep off the rain--just to grow lavender.