I agree it resembles sunburn but it isn't. I have had several leaves
look like that in areas where direct sun never touches. I have plants
with sunburn but not the Phals.

Steve

Ray wrote:

I see traces of sunburn (tan patches in the top photo), but the rest looks
like bacterial infection or something.

The pale yellow patches on otherwise OK-looking leaves is worrisome, but I
cannot say what's what.