I have three Japanese Maples Corral Bark and One Good Blood Maple. Ground cover is small black bark with a breathable weed cloth underneath. About 4 to 6 inches. Was watering in summer every fourth day about 1/2 gallon. Picture up close is of a maple where 1/2 of the tree appears to be dead. The other half is alive but yellowing. I stopped watering thinking maybe to much water. Only the lawn gets watered 4 min. every other day. We had sand stone for dirt. I have Bobcat out the dirt of 12 inches and replaced it with good soil about 3 years ago when I planted the trees. They were in 22 inch wooden crates. Other picture is of a Birch tree. 15 gallon. Grew great until this year. One of then started to droop. Leaves are turning brown. Other more mature trees are still green in the neighborhood. In the third Picture, you can see the maple in the background 1/2 dead 1/2 alive. The birch, 2 are fine 1 is drooping. The ground at the birch is hard. Unable to bobcat the dirt due to the wall and light restrictions. I have not fed then as of yet. Not sure what to do.
You need to find out if they are wet enough or too wet Dig a small hole beside one of the trees to test the soil I think they may need more water than half a gallon every 4 days in your temperatures, but you need to be sure An idea is to dig that type of hole and then fill it with gravel, and then top up that hole every day with water. That keeps a steady supply but never results in an overwatering situation
Several prune ,if your lawn received water in mornig or when the sun is high the leaves of maples are burn!See in top page FAQ "how plant a maple"and good luck!!