The picture is a bit fuzzy but I would guess that you have a problem with rust.  When you touch the  surface do the bumps  release tiny brown dust particles?  Rust spores can be spread many miles by the wind and develop quickly in humid weather.  I am sure our wet spring and early summer contributed to your problem.  In order to prevent contamination for next years plants it is critical to remove all infected plant material being careful not to spread the spores.  You might want to put a large plastic bag over the plants, bend them, down, and  cut them off at the base.  Be sure to pick up any leaves that might have already dropped to the ground. You do not want to put in your compost pile or any yard waste collection program.  Either burn if able of put in the garbage destined for a landfill.

Hopefully next year, depending on weather, you will have beautiful hollyhocks once again.