If they are covered in black spot then you must have started spraying after they first got infected (you can prevent but not stop once in the individual leaf). This is also why they have defoliated. Some varieties lose more leaves than others in response and the aspect and soil plus current conditions all play a part too.

Lightly prune and apply a slow release, high potash fertiliser around each plant. You may get some regrowth but by pruning lightly, this means you can cut back properly once the cold weather sets in and not have soft growth through winter that dies back and attracts fungi and disease that can cause die back in the stems. The high potash fertiliser also gives the plant a degree of resistance to black spot, mildew and rust though spraying is also necessary next year.

You could also try this if you want in early/late winter. Clear all fallen leaves from around the plants and apply a covering of compost a few inches thick if possible. This will form a seal over any remaining fallen spores on the soil and prevent rain splash sending spores back onto young growth next spring.