Hi- this is natural June drop (thinning) of excess peaches. You would have a full crop if only 5-10% of blossoms produced fruit. There should be about one peach diameter distance between fruits to ensure large peach size and reduce pest and disease issues.

The spotting of the fallen fruits could have been caused by fruits rubbing against other fruits and twigs and branches.  They do not appear to be caused by insects or diseases. Open some of the fruits with a sharp knife to look for Oriental fruit moth larvae. Plum curculio adults leave crescent-shaped scars on fruits while laying their eggs.

See more peach information:
https://extension.umd.edu/resource/growing-stone-fruits-home-garden-cherries-peaches-plums/
Jon