8yr old Rhodo, planted by porch near overhang. Dry clay soil. Sun late afternoon. Leaves are turning yellow with brown spots. Same thing happened last yr. Fertilized it 3x and sprayed with no wilt and it rallied. Bloomed and grew new leaves but 7 days ago the yellowing started again rapidly shedding leaves.
I expect your rhodo problem is related to the conditions in which it is living. Rhododendrons and many broad-leaved evergreens are generally sensitive to dry conditions. Rhododendrons prefer to grow in climates like those of Ireland and Victoria, BC. They need well-drained acidic soil, more constant root temperatures and PLENTY of water. We have had a very dry, hot summer and you already know that under the porch overhand in dry clay soil, the plants are dealing with drought conditions already.
To revive your plant in place, remove any dead or damaged branches and manage the plant according to the detailed instructions in the Culture page of the American Rhododendron Society website, an excellent resource: https://www.rhododendron.org/irrigation.htm Be sure to spread a layer of mulch around, but not touching, the base of your rhodo. This will help insulate the root system and stop heavy evaporation during the hot, dry conditions.
However, the location is not at all ideal … dry, clay and subject to the lime leaching from your concrete foundation. You may want to consider relocating the plant.