I have a beauitful pink azalea that is huge. It is about seven years old and has been so healthy. This spring I noticed the leaves on the center branches were all wilted and dried up. I cut them off but now it appears I am losing the rest of this huge bush. What could be wrong? I live in OK and have grown Azaleas for years with no problems. This was the largest and prettiest of them all. Do you know what could have caused me to lose this bush?