I need help to figure out what's going on with my Rhododendron. It is approximately 3 years old and for the past 2 years this one gets leaves and flowers on the end of the branches but the interior looks completely dead.

Any suggestions on what I can do to promote growth inside the plant? I fertilize with an acid miracle gro and it receives about 3-5 hours of sunlight daily. There is another one that's about 10 feet away that receives less sunlight and is thriving much more than this one.

Any suggestions are appreciated.

Needs a good pruning. Here's a good tutorial on pruning rhodies and azaleas.

https://youtu.be/5v7A_yWZcrw

Pic of this spring first pic azaleas others rhodies... they started out small and years later grew larger and more flowers .Some have grown to the size of small trees. Pruning can contain the size or larger depending on placement and use.