They need to recover from the hot summer days at night but cannot if the rocks are still keeping things warm. Use hardwood mulch, pine needles, etc.

As others have said, the rocks are crisping the plant up! It's like making pizza on a pizza stone. The stone helps to give you that crispy, crusty texture that people seem to enjoy.

and if in fact that is the issue ... then what you are seeing is all secondary .... if you dont fix the primary problem ... then all the secondary things dont really matter ....

ken

I think you should move the plant to another location in the shade, no rocks and away from the white wall! The reflected heat from the wall is even greater than direct sun. Here is a very long paper that explains how reflected sun - in shade - is hotter and more damaging than direct sun. Long paper but very well researched.

Daylight White Paper

Thanks everyone. I thought that the rocks may be a problem. I just didn't think that it could be this bad. Pulling the rocks back and mulching them was actually on my list but I will definitely do it sooner than later. The sulfer/iron was due to extreme whitening/yellowing in some leaves with dark green veins. Our soil here isn't very acidic. The leaves have greened up a bit so I think the browning/crisping is a separate issue and probably the rocks base on everyone's feedback on this and another forum. They are on the east side up against the house, against the house. They house is taupe vs white but a lighter color none-the-less. They only get early morning to early afternoon sun, then the house shades them the rest of the day. I figured this would be enough shade and the local nursery said the same thing. I have more experience with vegetable gardens than I do with flowers and bushes.

Color and reflection properties.
Here is the difference between the various shades of white and the reflection
as measured by a scientific light meter and the link to the study and author.

https://thelandofcolor.com/lrv-light-reflectance-value-of-paint-colors/