My Oakleaf Hydrangeas bloomed beautiful white flowers in June. In July they all turned brown and dry as if it was autumn. The leaves remain green with new growth of green leaves. They face East with afternoon sun. They are 5 years old and planted in amended clay soil. We are in a drought in Illinois but I check the soil for moisture and don't think they are too dry. The new growth is very healthy. No sign of fungus on leaves. Any advice would be appreciated. Thank you