Why do you think they are dying? Please be more descriptive. I believe you can water them heavily to try and reduce the toxin to save them.

Yes, rhododendrons are sodium sensitive plants. They don't do well when they get salt products containing sodium such as table salt. There are many plant safe salt products, but some are actually fertilizer and may cause fertilizer burn.

The advice to water heavily was excellent IF the plants have good drainage. If you do this, water heavily when it is cool and then let it drain thoroughly. You may have to cut drain paths about 8 to 10 inches deep outside the drip line where it won't damage the roots to improve the drainage. The roots are very shallow so don't dig near the plant.

PS:

Before flushing with water, remove all surface mulch and debris because it will have salt in it. Replace the mulch with new, salt-free mulch after flushing with water. Keep the old mulch away from any rhododendrons or azaleas.

Thanks for the input. I have performed these suggestions however, there are whole branches of curled brown leaves. Do I cut back or wait.