Get the Black Oil Sunflower seeds. The Zebras are less well liked. The oil ones are healthier for them also and they need the energy now that nesting season has started. 
I believe feeders with little pegs on them are the cause of the spread of disease in birds also. Cardinals prefer to scratch around in the leaves for their food. Other small birds will prefer a small flat surface with seeds on it, like a little yard table, and the sun will keep it sterilized. You might want to get a sock feeder for Niger seed for the goldfinches and other small birds.
