Amur Maple -- Leaf Yellowing

[xRainy]

We planted this Amur Maple (Acer ginnala Ruby Slippers) in April/May of this year with root growth stimulator from the nursery. The Maple has grown over a foot in height since planting and has increased noticeably in diameter in that time. However, I have been noticing some recent yellowing of leaves of of multiple branches as well as the death of one smaller twig as shown in the images. Many leaves appear tattered along their outside edges. We live in Oklahoma, so there has been long stretches of 100+ degree weather. We have been watering the Maple every other day for 30 minutes within the mulch ring's borders. We do have cicadas active in the area.

 

Would anyone have any advice or recognize this type of damage? We are open to changing our watering schedule or method if this is potentially heat scorch or underwatering. Aside from some small ants on the trunk of the tree, I did not notice any aphids or obvious clusters of insects, unless they are better hidden. Thank you for your time.