British Columbia: Wilting rhodo

We have an elderly medium/large rhodo that seems now to have continuously wilting, slightly yellowish leaves. In the past, it came through the winter looking like this then recovered but it hasn't recovered yet this year (June 2010). It still, however, has blossomed profusedly. Does anyone know what might be causing it to look so wan? It is getting watered reqularly and the similar size rhodo next to it looks as healthy as ever.

 

Probably a problem at the root, like root rot or honey fungus.

 

should I hoick it?

 

Dig around the roots and look for clues, like soggy/dusty soil, lots of dead roots, honey fungus 'bootlaces'...