Hi David,

This looks like stink bug damage. See the stink bug information on this page:

https://hgic.clemson.edu/factsheet/peach-insect-pests/

Next year, you may want to consider bagging some peaches on the tree to protect them. Plastic sandwich bags are commonly used as an organic way to protect apples from bugs by home gardeners. I'd be concerned that softer fruit like peaches might fry in a plastic bag, but there are cloth, paper and net fruit bags on the market. Some people also use old nylons, tied on the fruit. The fruits are bagged when they're small, before insects have a chance to get to them.

Sorry I don't have a better solution. Good luck.