Sorry I am not familiar with the redbud tree, but searched on the Extension websites to see if a similar question had been researched.  Here's a great answer from Virginia Master Gardeners:  https://piedmontmastergardeners.org/article/whats-wrong-with-our-redbud/

Here is an extensive article from an online nursery:  https://www.gardenia.net/guide/redbud-tree-pests-and-diseases

From scanning those two articles, your tree may be suffering from a disease such as wilt, so follow the information provided.  And just as a reminder, when you water, water deeply (let the hose or sprinkler run until the water has reached deeply to the roots, not just at the top inch of soil).  

Here's a response from a 2019 Ask Extension question about a similar problem:  

It's possible that the redbud is dying from drought, which dies up and kills roots. We see that it has some very surface roots, which suggests that the soil is hard or poor below. In that case, water deeply through fall (many droughts extend into fall.)

It could also be a disease, Botryosphaeria, which you can't treat. It is associated with drought. It will die eventually.

In any case, prune out totally dead branches. To determine whether a branch is dead, scratch the bark and look for green tissue underneath. Green indicates it is still alive.

You may want to see how it goes next spring. If it has lost too much of its canopy, replace it.

EllenAnswered by the Home & Garden Information Center's Maryland Certified Professional Horticulturists Replied August 19, 2019, 11:32 AM

Good luck with your tree!