Coat 3 mini loaf pans (5 3/4″ x 3 3/4″) with nonstick spray. In a large bowl, whisk together flour, baking powder, baking soda, salt, and cinnamon. Make a well in the center of the mixture. In a medium bowl, combine the buttermilk, egg, coconut (or vegetable oil), brown sugar, and vanilla. Add wet ingredients to flour mixture and stir just until combined. Gently fold in diced peaches.