Hi, 

Redbuds, while being beautiful early spring bloomers and lovely native trees can come with their share of issues. They can be prone to verticillium wilt, Botryosphaeria, and leaf anthracnose (although this doesn't appear to be anthracnose symptoms).

Stressed trees can be more susceptible to contracting a disease and could have predisposed the tree(s) to infection or dieback. Root dieback alone from environmental stressors could be at play and not a secondary disease. They could have been over-watered, under-watered, stress from urban and suburban growing conditions (heat, drought, compacted soil, salt spray, herbicide drift from neighbors etc). It can be difficult to tell because symptoms overlap quite a bit, why we can't nail-down a specific cause from its appearance alone. You can check lower on the tree for borer holes. You can trim out the dead branches, and if possible make sure they are receiving adequate water. If tree gators or donuts are available that could be helpful for watering needs if a hose can't reach the base of the trees. Just keep monitoring for further symptoms or new growth. 

If it comes to planting a replacement tree you can always refer to our  Planting a Tree or Shrub page although you probably are already versed in this with the program (root flare depth, loosening roots upon planting, not mulch up against the trunk but mulch around the base of the tree so mowers and trimmers don't hot the trunk etc.)

If all redbuds were planted and not a lot of variety in the trees, maybe offering up some more variety of less susceptible trees would be good! Many people want flowering trees but planting a mono-culture can result in a disease, pest, or extreme weather event taking out the trees all at once. 

Let us know if we can assist further or offer replacement suggestions. 

Emily