I just walked out and checked mine, no marks like that. But it could be cold damage from winter's chilly nights.
Watch for new growth, and if it is healthy and green, I wouldn't worry about that brown mottling as long as it's not spreading up the stems.
Btw. mine is growing in partial shade, but does get some direct sun in the early afternoons. My neighbor is growing one in almost full sun, so I don't think heat or sun should damage it like that.
