Oh, what a shame, Mary. I'd suggest you empty the soil out of that EB, clean it completely with soap and bleach, and start with fresh potting mix for your next planting. You can try for more tomatoes starting in February. Start your own seeds in early January, which will be cheaper and safer than buying transplants.
That looks more like a blight infection to me than herbicide. If it was herbicide drift, your broccoli and cabbage would have died as well. It may have been from wherever you bought your transplants, but wherever the blight came from, it has surely infected the soil in there again.
