m0useanswered grow question 3 years ago get a magnifying glass and check the under side of the leaves.
could be mites.
close up of what to be looking for.
https://gardenerspath.com/wp-content/uploads/2021/06/Spider-Mite-Eggs-on-the-Underside-of-a-Leaf.jpg
https://www.growweedeasy.com/wp-content/uploads/2013/07/two-spotted-spider-mites-with-eggs.jpg
once you rule that out then you can think about light bleaching or nutrient/substrate issues
best of luck