New Growth Branches Falling Off Crape Myrtles?

I have two crape myrtles that are 10-15 feet tall. I have never had a problem until this year. I'm noticing small, new growth limbs (6-12 inches long) falling off. The limbs are full of green leaves, though the leaves have become soft and droopy. I'm losing about 3-4 such limbs per day, though the remaining limbs all look healthy (for the moment). We just had our front yard re-sodded, and have to water 2x per day. Could this be the cause for the loss of these healthy looking limbs?

Hardiness Zone: 9a

By Mike from Austin, TX