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What is the extent of the damage? Have you spotted any insects chomping away on the leaves? If so, do you have a photo you can share? One of the most notorious insects that devour peach tree leaves is the japanese beetle. For more information on the japanese beetle, please visit the following link:
https://www.gardeningknowhow.com/plant-problems/pests/insects/japanese-beetles.htm

This article will help you:
https://www.gardeningknowhow.com/edible/fruits/peach/peach-tree-fruit-drop.htm

Do your tree previously produce normal looking fruit?

You could have purchased a mislabeled tree. I worked in a garden center, and yes, it does happen.

Also it's possible that your tree is grafted unto another root stock. This could be a different fruit species.
Here are a couple links to help you out.
If possible send us a picture of the fruit growing on your tree.

https://www.gardeningknowhow.com/edible/fruits/peach/peach-tree-care.htm

https://www.gardeningknowhow.com/ornamental/trees/tgen/can-grafted-trees-revert-to-their-root-stock.htm

There could be many reasons your tree is not bearing fruit.

Here is a great article that will help you pinpoint the growing issues with Peach tree.

https://www.gardeningknowhow.com/edible/fruits/peach/tree-with-no-peaches.htm

I need to know if I can spray fixed copper or some other spray preferably organic on a peach tree with leaf curl that is leafed out and has fruit developing on it now.

Maybe things aren't so dire - is there one fruit every 6-8 inches? If so, you thinned it correctly and will be just fine. A peach tree goes through distinct sequential stages every season (http://www.pearsonfarm.com/blog/the-yearly-growth-stages-of-a-peach-tree/). I think by this point that the bulk of the fruit the tree was to produce would have formed.

For more information on peach tree thinning, please visit the following link:
https://www.gardeningknowhow.com/edible/fruits/peach/peach-tree-thinning.htm