Plant Doctor

I think I need a plant doctor. Does anybody know anything about Rhododendrons? We have 4 big ones in front of our house and they are really the anchors of our front landscaping. They have probably been there as long as the house (10 years) and I fear that they are sick. Two of them look healthy like this:


But two others look more like this:


I also noticed this same affliction happening to several of the Rhododendrons at work so I guess I'm not alone. Is this normal for the Spring? Will they magically come back to life? Do I need a plant doctor?

But on a brighter note, I also found a few of these in the yard today. And that makes me very happy!