Carolyn:  Thank you for contacting the UVM Extension Master Gardener Helpline with your question as to why your peach leaves are disfigured.   Your attached photos helped in identifying the problem.  This is Peach leaf curl, which is a fungus that affects peach trees. The fungus survives the winter on the surface of the twigs and buds, and affects the leaves in the spring. The leaves will curl, may turn reddish or purple to gray,  and eventually turn yellow and drop off.  Note that the new leaves produced later in the growing season (June or July) will not be affected.  

This condition usually happens during a cool, wet, spring, following a mild winter.  It is a hit-or-miss condition.  Some years we see it, and some years we don't. This seems to be a year that trees are affected.  We are just now receiving questions coming into our helpline from people experiencing this same problem as you are seeing.  

Treatment is fairly simple, but it is too late to treat for the fungus now.  If you have a significant leaf-drop this summer, you may want to thin the fruit to reduce the crop and reduce the demand on the tree, which may lessen the chance of winter injury.  A fungicide application in the fall, or very early in the spring (before the buds swell) is recommended to prevent the problem from occurring again.   Below are links to information from Extension sites for Ohio State and University of Illinois to further explain the fungus, and also to provide you with information on recommended fungicides for the problem.

Peach Leaf Curl | Ohioline (osu.edu)

https://extension.illinois.edu/blogs/good-growing/2020-03-11-peach-leaf-curl

In addition to the recommendations above, you should also rake up any dropped leaves and fruit during the season.  Pruning the trees during the winter dormancy period will open up the tree to air circulation, and light penetration.  The fact sheet from the University of Minnesota, below, contains tips on pruning peach trees.

Growing stone fruits in the home garden | UMN Extension

I hope you find this information helpful.  



Good question, Carolyn.  The Home Fruit Production fact sheet from Missouri Extension, attached below, suggests thinning peaches to eight inches apart, even if the tree is not affected with leaf curl.  This is because a peach tree will normally set a lot of fruit, and without thinning, the peaches will be smaller.  You should thin them now.

Home Fruit Production: Peach and Nectarine Culture | MU Extension (missouri.edu)