Most of the time black spots on leaves of Draculas are due to heat stress. Draculas are cool growers and daytime highs in the 70'S is pushing it...let alone 80's. I had a few in the kitchen last year and the leaves were slowly consumed by these spots. I moved them all to the basment with my Masdevallias (daytime highs of 68) and they are growing great, no more black spots. A fan gently moving the air may help a bit if you dont have a cool grow area. I also know someone that encloses their Dracs in a 10 gallon aquarium with icepacks during the hot summer days.