Tracks of yellow on Phal leaves

[bethmarie]

None of the pictures I've seen of fungus/bacteria/pest infected leaves match the track pattern of yellow on this plant. A couple of the Phals I ordered this summer arrived with mesophyll cell collapse. The one pictured below also shipped during high heat, but does not have sunken areas of collapsed cells, just this yellow tracking on all four leaves, some worse than others.

I haven't seen this before, and wonder if someone here might have.

Thanks