Rhododendrons, although evergreen plants, do lose some of their leaves. Sometimes the leaves turn yellow, but they can also be surprisingly bright colors before dropping...yours will drop when they are ready. As long as you aren't seeing something odd with this last seasons growth, you have nothing to be concerned about.

Most varieties hold their leaves for two years and then in the third year, as summer progresses and days shorten, the lower leaves turn color and drop off the stems.

My PJMs leaves actually look almost blackish-purple. This is the first year I've had them so I hope its just the change of the season.

PJM colors up nicely for me every year in the fall. Here's a picture of mine I took a few days ago. It is one of my favorites.

Here is a link that might be useful: PJM Rhododendron

My rhododendron has changed from a white flowering one to a pink. How is that possible? It hasn't bloomed since I bought it two years ago and has pink buds this year. Is it caused by the chemical composition of the soil? Thanks for any information.

I only know of one variety of rhododendron that has white buds and white flowers. All the other "white" rhododendrons have pink or red buds that open to pinkish white or white flowers. The Yaks are the most famous for this. They always open pink and fade to white.

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Album Elegans fades to white

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Catawbiense Album has pink buds that open and fade to white

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R. maximum has a fair amount of pink even when it blooms

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Boule de Neige opens white, the only hardy white I know that does.

Thanks for the info. Maybe it will be white when it blooms then. I wanted a white one, got it and have waited two years for it to bloom. Winters are hard here in Maine but it has survived.

Thanks for the info rhodyman, that is pretty interesting. I haven't studied the whites carefully but now that I think about it, it does almost always seem that they are another color in bud. Even though I prefer certain colors I want to have some white and purples in my garden for contrast. Rarefind has an amazing 'Gable's Hardy White' [decorum] which I believe would be hardy for you in zn 6 with ridiculously gigantic white flowers. I saw it touring the display gardens but forgot to get it when I was purchasing plants! That's a dangerous place to shop in May if you like rhododendrons...I alway spend at least 50% than I wanted to.
One of the only whites I currently own is "Silver Sovereign".