http://www.organicgardentips.com/how_to_grow_azaleas.html There's a lot of info on this page. I know that I have mine in the shade and prune them right after they bloom. I had a few that had yellow looking leaves last year and I added some fertilizer around the roots and they perked back up. How long have you had these? Could they be bad plants?
I've had them for a few months now. Got all the plants at the same place/time. And planted all at the same time. This one bloomed beautifully right after planting, and so did the others. But ever since I treated it...it's gone downhill. And it's the ONLY one that did! All the others are perking up from the treatment.