We probably need a lot more information (where is it growing -- soil type -- watering -- things like that) but at first look, it could be sun damage/drought. Is it in full sun? What kind of watering does it get (for example, if it's under the eaves a house it may not get enough water from rainfall).

It could be a disease, too, but it's hard to tell from the photo. I would hesitate to tell you to do anything to the plant to address the problem without knowing exactly what's wrong.

Rhododendrons tend to have problems in the Midwest; they just don't thrive here like they do in some areas of the country, but they sure can be beautiful.

If you have a local master gardener clinic, take some good photos (like the one you have and some close ups) and a good sized piece of the plant (leaves and stem) and take it in to the clinic. They should ask you a whole bunch of questions that will help them figure out the problem. Or, if there's a garden center you especially trust and know, do the same with them.

Sorry I don't have a better answer; good luck!

As a PS, you might post in the rhodie forum... see link. Folks there might be able to help more! Good luck...

Here is a link that might be useful: rhodie forum

Thanks for the replies. I just moved into the house and don't now anything about what was done before. I have only fertilized and mulched. Its not in full sun. I will try to get some better pictures and post in the rhodie forum. Thanks!
-David