We planted a few purple gem rhododendron in the late spring of 2021. They did great in 2022, all blooming and growing larger.

Until November 2022, when 2 of them suddenly had issues. The first one died and the second has not really had any growth this year and looks paler green.

Those issues are now happening to 2 others this year and it happens suddenly. On July 20, they were ok.

Here is one on July 21. Generally healthy, but notice the yellow patches

And its getting worse by July 23. And another plant now has started the issue, but much worse

And worse by July 24

Still worse on July 25

As of July 29, both are getting more dead patches

Any idea why this keeps happening, especially so suddenly? And what can be done about it?

Please help.... and thank you in advance...