Hi Kyla, I assume there has not been any construction around the tree that might have caused root injury? Redbud can get a couple fungal leaf diseases that can cause leaf drop. Unfortunately they also can get a more serious disease of verticillium wilt. At this point I think your best bet is general good care as in mulching, watering during drought (if it would ever stop raining) If it seemed fine last year trees ceratinly have the abilty to releaf if they are in generally good health. as long as the stems are still green there is still hope they will releaf. good luck, sandy