The leaf damage does not look like leaf blight. It looks more like a caterpillar chewed on the leaf when it was young and still curled up. Look on the underside of the foliage for a small green worm or caterpillar. I do notice the leaf had dark green veins and is a bit mottled. This could be from lack of iron or another nutrient. Most trees do not need fertilizer but in this case with your young tree I recommend you add a teaspoon or two of Osmocote around the base of the tree and work it very lightly into the soil. Remember when it comes to trees and shrubs the first year the sleep, the second year they creep and the third year they leap from the ground. Keep growing - and thanks for watching the videos, Marianne Binetti