The stems, leaf stalks, and the bottoms of the leaves of the hollyhocks in my garden are filled with orange-black blisters. The leaves eventually dry up and fall off. The blooms are not affected.
Your hollyhocks, like most, are suffering from rust. This is a common fungal disease on hollyhocks. Sanitation and proper planting may help reduce the problem. Remove and destroy all infected plant material in the fall. Make sure your hollyhocks are growing in full sun with plenty of room and good air circulation. I often plant other flowers in front of my hollyhocks to mask the damaged leaves. For totally disease free plants you can use a fungicide labeled to control rust on flowers. And as always read and follow label directions.