This is a young tree and the pattern suggests stress damage. Check the underside of the leaves for aphids or leafrollers (will see webbing). Excess water may cause this also. More likely given the current weather is that the plants is not getting adequate water. Mulching can help, but not near the trunk. The root system may take 3 years to mature. In this heat wave, you should be watering weekly in the canopy area. You might want to test the moisture in the soil 24 hours after watering and be sure it is going deep enough.