There are several contagious diseases that can be passed among birds that come to bird feeders. This is especially true if the feeders are the style where the birds can stand in the food itself (like a tray feeder or seed spread on the ground). First, take down the feeder for a week or more and wash it in a 10% bleach solution. Second, let it dry and then put it back up in a somewhat different place (if the problem is food accumulating on the ground under the feeder). Moving it by even 10 feet is enough to shift the birds away from the accumulated material.
The diseases that birds can get at feeders have scary names (like avian salmonella), but they are not the same strains that humans get. It is NOT “avian flu.” In spite of dire government warnings, avian flu has not been detected anywhere in the Western Hemisphere, much less in Indiana.