I can't find a nursery within 70 miles of Moore County, NC that has Rhododendrons for sale. They all say the Rhodies have or get some kind of disease. What could be the problem?
I would contact your local County Extension Office and inquire if any local issues have been reported with Rhododedron's.
My research did not find any current reports of new diseases.
Here is a link to help you locate your closest office.
Here are some other articles with more information.