Peach Tree Disease
This looks like brown rot on the peaches. This is common on peaches and requires a spray schedule for control. All you can do is remove and discard the fruit. It is too late to spray. http://extension.umd.edu/hgic/diseases-stone-fruit
Many cycles of infection can occur in one growing season and ripening fruits are most vulnerable to infection. A protective fungicide barrier is critical from prebloom through preharvest. At least, remove and dispose of fruit mummies from the ground and from trees and always try to remove fruit stems attached to the mummies, if a problem.
Tree fruits can be a challenge to grow for the average homeowner. Peaches tend to have several pest and disease problems and they need to be on a strict spray schedule. You will have to educate yourself on preventing and managing the most serious disease and pest problems. For general information see our website on stone fruit http://extension.umd.edu/hgic/planting-and-care-peaches-cherries-plums-apricots-nectarines
and the Va Tech Spray Schedule http://extension.umd.edu/hgic/plants/tree-fruits-pest-control-and-spray-schedules