How much/how long are you watering? By 'drip ring' do you mean like a soaker hose surrounding the base? Or a real drip emitter system? Red maples have a huge geographic range that covers some very warm climates but they do prefer a moist soil. In fact, one of their common names is "swamp maple". I would expect the wilty looking foliage is just telling you these trees are not getting enough water.

It is a drip emitter system. Two hours at a time 10 gal total per tree every three days.

Where are you/what climate are you in?

Have you felt two inches down into the soil on non-water days to see how much moisture your soil is holding? Relying on timing or even gallons to determine watering needs without feeling the soil can be misleading. If it is draining too quickly or you are getting run off the trees will suffer.

It's hard to tell from the photo, but the entire area looks parched. Perhaps your rings are too small and missing the periphery of the root mass?

Feel the soil. They look thirsty.

We are in zone 9a --20 mi east of San Francisco so we have the Marine in Fluence however our summer temps are reliably in the 80s and 90s. We have clay soil and so yes without any landscaping the earth looks parched. We amended the soil when we planted the trees. And I have dug down 6 to 8 inches and it is moist, but I don't know how well it's draining below that. About three weeks ago we did enlarge the drip circle width so that they are almost to the canopy. I just put a 2 to 4 inch mulch above the drip lines/canopy.