I would check that your problem is not Peach Leaf Curl.
If that's not the problem then it may just be that the roots cannot replace the water the leaves are transperating in the sudden wamth.
Keep the watering up and if possable give the tree some shade from direct sunlight.
When the trees roots are not big enough to replace the water that the leaves are ' sweating ' off ..they can dessicate as a result.
In extreme cases it may need the top reduced to give the plant a chance.