Hi there! We inherited a rhododendron plant from the previous tenant of our flat; this is how it looks:
Is it dead? It has yet to bloom, and the leaves don't look very healthy.
It could be dehydrated or starving or both. Give it a feed with Ericaceous plant food and water it regularly. It's quite big for a pot so it will need a bit more attention than if it was in the ground. You can also get a foliar feed for rhodies and azaleas. Might do no harm to try that as well.
Epsom salts??? Really????? Well I never!
Agree with plant pauper; it is a lot of plant for the pot. Give it a good feed (suitable for lime hating plants) and water regularly. Do not use tap water as the odds are it will be hard i.e. alkaline. Yellowing leaves are symptomatic of chlorosis, the chief causes being wrong pH and nutrient deficiency. Some chelated iron feed should help.