Did you plant them or did someone plant them for you? If you have been giving them ample water, maybe you should carefully dig around the root zone to see if they were planted badly, which is an all-too-common cause of death in newly planted trees.

Was it balled and burlapped, and were the burlap and cage removed priot to planting? Were the roots teased out and untangled so they won't be girdling circles around the root ball? If you dig down and find an air gap between the root ball and the surrounding soil, like I did with a Swamp White Oak a few years ago, you might be able to bring this tree back in short order. Soak the soil all around and beyond the root ball. Get rid of that air gap. I did it by hand tilling the soil, carefully ungirdling some roots and then mixing it all up, adding some compost around the roots and a couple feet beyond , and then mulching. Water it one more time.

It took over an hour in blazing heat, and I gave the nursery a well-deserved tongue lashing. I could have had them come out and fix the problem, but it was pretty obvious to me they didn't know shinola about how to plant a tree.

My seemingly dead/defoliated oak releafed within a few weeks, and today it is gorgeous. Good luck.