seilMI said:Where do you live? What kind of weather have you had over the past 6 or 8 weeks? Have you used any chemicals or fertilizers? There are many reasons why a bloom can change its form. Without further information it would be hard to say what it might be.
Black spot is not a bacteria. It is a fungal disease. You can remove the spotted leaves but that will not prevent it from returning. There are fungicide sprays you can use but they take time and repeated uses. It would help if you cleared out all the grass around the base of the plant for at leat a foot away.