The blisters are appearing in exactly and only in the areas where I brushed up against the plant. I felt the quick little sting when I brushed up against it at the time (similar to brushing up against a thistle or rosebush - like small, innocuous scratches), which only developed into blisters the next day. I have no known allergies (plant, food, latex, etc). Though maybe I have a special sensitivity to whatever this plant is! Thanks for the help!! :)

You sure have honeybees! If you want to take them out alive the siding have to be removed to get axes to the hive. See if a bee keeper is willing to do the job and how much..$ Konrad

Also known as Heal-all, Prunella vulgaris is used in herbal medicine and the leaves are edible.

Try watering daily for a while and skipping the fertilizer and see if that helps.