Not enough water. Cercis occidentalis are native to seasonal creeks in dry areas, so in spring when they are pushing out their flowers and then new foliage they are getting a good amount of water, and as they mature can send roots down deep to what soil remains somewhat moist in the streambeds to get through the summer.

Your plants need to be more established to handle low amounts of summer water. Low water requirements once established. They need to get established first.

Lamb's Ears, have never had luck with them. Killed many.

I bought 5 redbuds from Arbor Day Foundation. They came to me as bare root sticks about 12" tall. I planted them in fall of 2014. Three of them are over 6' tall, 1 merely a foot tall and the other died. These 3 are planted in close proximity to each other and the 1 not doing so well is planted maybe 30' away. I think the different soils make a huge difference. They are on a drip system and I have been watering them about every 3 days for a couple of hours this summer. Been pretty hot here in norther California.

woody plants need at least 2 years of regularly scheduled irrigation in order to establish a vigorous root system.

Drought tolerant plants are not instantly drought tolerant. They need water to establish a good root system, and then water can be reduced. That takes more than a year, depending on the time of year you planted them. Both of your plants look extremely dry. You should also have a woody mulch to keep moisture in the ground. Mulch should be kept 6 inches from the trunk to avoid rotting the trunk.