Stone fruit are turning mouldy on a healthy tree?

Question

I have two peach trees, and they have flowered well with good fruit set, but as the fruit has matured several of the peaches have become shriveled and moldy.

Answer 1

I recommend dormant spraying with a horticulural oil and copper fungicide. And then during fruit set start preventive treatments with a biological fungicide like this:
https://shop.nutri-tech.com.au/products/tricho-shield

Good soil fertility and water management will help the trees and fruit resist diseases and pests.