It is hard to tell in this photo.  Do you see any insect damage or fungus?  I recommend you bring a sample to our office.  You can bring a branch to our office or send more photos.  keisha.bruce.uku.edu or 4200 Gardiner View Ave Suite 101. 40213.  

It needs to be mostly living with samples of disease.  We can identify the issue in the office and/or send to the lab.  Feel free to call the office at 502.569.2344.