Nice looking zamal, wily. I had stippling like that on some of my leaves and it turned out I had mites (two spotted in my case). Have you checked the undersides of those leaves with a loupe? If not, you might want to take a closer look.
HB.
I am everyday in war with mites, and many other insect, i spray the plants with a solution of hydrogen peroxide, I think it's h2o2 ...they go away but after 3-4 week come back...