Gardening: Leaf curl on Redbud
You did not mention how old the tree is, planting techniques, etc.
Your redbud sounds like it was susceptible to a type of stress. When trees are subject to this they can take on a reddish type color. Leaf curl can be attributed to excessive moisture (which we have had a lot of), poor drainage, dry periods, etc.
Also, you can look for any insect issues on the foliage and dark sunken areas on the branches or trunk.
Make sure your mulch layer isn't too deep (no more than 2-3" of mulch and avoid putting mulch right up to the base of the plant). At this late in the growing season, trees have stored sufficient carbohydrate food reserves and they can tolerate some leaf damage. No control is necessary. Monitor the tree and if you are noticing additional symptoms, you can send us photos so we can see what you may be dealing with.