The source of water is probably doing more to affect the pH than your fertilizer. Use rainwater, water from the dehumidifier or distilled water to help with soil acidity. Hello Linda, Blackspot causes the symptoms you described. Remove infected leaves as soon as they appear. Fall cleanup is also very important.
Infected leaves increase the source and risk of disease.
Fungicide sprays will reduce infection. They protect uninfected leaves. Weekly treatments with a fungicide labeled for use on blackspot will reduce problems. Read and follow all label directions carefully. In late spring I had white foamy substance on most of my flowers.