It looks like residue from insecticide
or fungicide applications; or, early on, the plant was in a situation
where it was watered from overhead and the water was allowed to
repeatedly dry on the foliage, leaving dissolved solids residue on the
foliage. It's possible too, that the same chemicals mentioned above were
injected into the water used for over-head watering and were left
behind on foliage as the water dried. I don't think it's cause for
concern. If it interferes with the plant's ability to carry on photo
synthesis, chemical messengers will inform plant central the leaves
aren't carrying their weight, and the plant will automatically shed
them. Too, your plant looks healthy enough that removing the affected
leaves shouldn't create a scenario where the plant is using more energy
than it's creating by turning the sun's energy into food ..... so you
can remove them w/o need to be concerned. Remove them by snipping
through the petiole (leaf stem) about half-way between where it's
attached to the stem and where it transitions to the leaf blade. The
stub you leave will fall off on its own in a week or two. Pulling leaves
off can easily damage latent buds resting in leaf axils (angle formed
by a leaf and the branch it's attached to).

Al