British Columbia: Red Leaves on Rhodos

Hi there. I have just moved into a new garden in Vancouver with some rhododendrons that have been planted about 4 years. They are in an area with north exposure and morning sun and afternoon shade. They flowered nicely in May. The leaves on 2 of the bushes are turning red. Can anyone tell me if there is something I should be doing about this?

 

Could you get a closer picture of the affected leaves? That would make it easier to see exactly what is going on.

Thanks

 

Here are some closeup photos of the top and underside of the leaves. Thanks for anything anyone can tell me.

 

Could this discoloration be a symptom of a chemical deficiency, such as phosphorus or potassium?

 

It looks most like a chemical deficiency to me. The discoloration doesn't quite match most of the standard rhododendron leaf patterns of damage for other things. It appears to be either a nutrient that is lacking, or, just barely, a red phase of the common splattered/stippled pattern that is seen from a toxic chemical that drifts onto the leaves (i.e. herbicide mist, but not limited to things that are labeled herbicides). Usually, that is seen more as yellow stippling, not red. But different rhododendrons show different colors.

The next step is to find pictures which show common deficiency signs on leaves in general and see what matches the rhododendron leaves.