Answer: Some of this might be related to sun and heat and some to transplant shock, some to other causes. Rhododendrons do better if planted in morning sun or very bright dappled light all day. I would not recommend a location with hot afternoon-only sun. So you might want to transplant it, yes. If it has just been planted, you could still move it right now. I would not wait because the hot weather of summer is almost here and is very stressful on new plants so the sooner the better.
The discolored foliage could be related to a variety of causes, but with a new plant I tend to suspect it was planted too deep and/or over or under watered. This plant is very shallow rooted and should be planted no deeper than it grew in the container, perhaps even a half inch higher.
The soil should be organic and humusy and acidic, it should be evenly damp like a wrung out sponge,never saturated or sopping wet. To know if you need to water, dig into the soil with your finger. If it is still damp, do not water yet. Avoid wetting the foliage when you water. It is better to water less often but deeply than to sprinkle lightly every day. You need to make sure the soil is damp like a wrung out sponge, down about six inches.
Mulch over the root area with an organic mulch several inches deep, no deeper. The reason it should be a light layer is that this plant needs air at the roots as well as moisture. With too much mulch it will send roots upward in search of air, and roots growing in mulch are not as well insulated in winter as they would be grown in soil. This can lead to winter damage.
This plant is subject so some diseases that can cause foliage symptoms. So I would also recommend you take some photos of the overall plant and also close-ups of the affected leaves (or sample leaves in a clear plastic bag and kept cool so they do not wilt too much) and take those to consult with your retailer and/or county extension to try to get a specific diagnosis of the problem, in case it is a disease issue instead of or in addition to transplant shock. I hope it is nothing serious. Good luck with your rhodie!
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