Prune immediately after bloom and not in August. But: why do they look leggy in the first place? Too much shade? Lace bug damage? Foliage mildew?

Time to get a new one. Has it ever looked as full as it was in the nursery? How did look in the month of June? If it looked that way towards the beginning of spring to summer it’s dead.

Not sure why Claire L. Is suggesting it is dead. Rhodies respond well to hard pruning, though it may take a couple of seasons to fill in. They have dormant buds on the stems that send out new shoots.

I second Embo’s questions. Some Rhodies have a habit that tends to be leggy, but there may be a cause of its unhappiness. Generally where are you located? Do you have acid soil? What has precipitation been like this summer? Can you add a couple of photos in the comments (you may need to reduce the photo size for them to load), one of the whole shrub and its setting and one a closeup of some of the leaves?

To me when a bush looks leggy that means the branches are pretty much empty no leaves or flowers

Yes but the question is how long has it been leggy???!

Leggy usually means leaves and flowers only at the top ie bare legs.