That looks exactly like what we get here from sun and heat damage.

That said, I haven't gardened in your region. Even so, winter cold may be very similar to heat damage I just described.

In any event, the damage is environmental. The yellowing is more likely to be partial damage to leaf cells rather than continuing damage.

Unless, of course, you have cold damage to the roots or base of the stem. May need to take a very close look near soil level.

Your rhododendrons don't look nice at all. Did you planted them in acid soil with good drainage, peat a.s.o. and did you give them a lot of water? Of course you could try to cut them down a bit, feed them and give much water and see will happen.
I have problems with both Cunningham's White and Cunningham's Blush! And have had so since I bought them. About 60% or more of the buds don't open. And that happens both after mild and cold winters. All my other rhododendrons are okey!
Anyone out there who has healthy and freeflowering Cunninghams?

The soil was at about 6.5 last fall, not ideal I know, though C.W. is billed to be more tolerant than most. I added some sulfur earlier this spring. I amended with humus compost. The soil itself was good black dirt....light and friable. I haven't watered at all this spring since we're already ahead a few inches on rain. Should I prune anything that's browning?

Looks like classic winter burn - sun, wind, cold. It's possible that last fall's replanting stimulated late growth which was particularly vulnerable to Z5 cold, but lat winter was a particularly harsh one for rhododendrons in all frigid regions. The new growth buds at the terminals and up and down the stems looks entirely healthy. Cunningham's White, in my experience, does not care much for full sun even if it's just in the morning. Full sun leads to the lighter leaf color you've noticed.

Thanks for the replies. Would daconil be a good fungicide? I've never used fungicide before and I'm a chemical illiterate (aside from potable alcohol, of course). It seems as though newer growth is having issues so I'd like to get something on them before the plants are lost altogether.

Spraying is seldom effective. It definitely won't undue the damage you have. Probably a little shade would be best. The damage is sun burn. The spots are a fungus that infects the areas that already burned. The burning is worst when the soil is dry or frozen.

I planted mine early last year, and I think mine also had winterburn, though it only gets very early morning sunlight. I think I'll cover this time around with burlap for the winter months.

I have it tucked into a corner between my house and a fence on a north facing wall. I have had many buds last year, one solitary bloom I noticed as I was watering, I then walked over to my neighbor to show her the bloom, came back and it already closed up from my watering, just like that. I thought I was going crazy...I swear there was a bloom a minute ago! But, no buds this year, only nice new growth. Hopefully next year I'll see blooms.

Covering with burlap is a misnomer. The plants are actually protected which means that the sides are protected and the top is left open. The winter sun and wind are the culprits. They both come from the side, not the top. It is best to leave the top open.

The lack of bloom may be due to the lack of sun.

UPDATE

These CWs are trying really hard, setting new buds and leaves, but the latter are quickly browning (from sunburn I assume as the wall-side leaves are fine). I'm thinking of transplanting it to the north side of my house where it would recieve a couple hours of morning sun and a couple hours of evening sun instead of full sun until about 12:30-1:00 (I'm talking summer solstice hours). Our neighbor's house is no more than 8' away (in other words it's sort of an alley. I haven't paid too much attention as to whether this creates a wind tunnel or protects the area from the wind).

So my question is whether it is worthwhile to transplant them to this site? And if so should I wait until fall and allow the summer sun to work them over until then or transplant them now and let the heat do its work. It's not as though this is a high profile spot to my yard. I barely ever pass it except when I mow, but I have a hell of a time giving up on something that hasn't given up on itself.

Since they are stressed, it would be best to wait until fall to transplant. Then mulch well so the frost won't heave them out of the ground.

Here is a link that might be useful: How to grow rhododendrons and azaleas.

Thanks again rhodyman.