It looks like iris leaf spot, a common fungal disease on bearded iris. Encouraged by wet weather - which we have in abundance in spring - controlling it hinges on good garden sanitation, proper spacing for good air flow and planting in full sun. Removal of all affected foliage and any associated debris in fall will help.

You can find various online articles that go into it in depth as well as offering a few chemical control options.

Thanks Gardengal.