Silberne Flecken auf Blättern

Did you inspect under magnification? Some you can't even see with naked eye. Other are 1/20th of a inch in size. Pest are in various sizes.

If the plants overall health is good, and you can't find any bugs after inspecting the plant and looking on the undersides of the leaves, then i'd say just leave it alone and monitor closely for progression if any. Don't pick the leaf off just leave it on the plant. People often think that if they pick off a affected leaf that somehow they eliminated the problem. But what i find, is that instead of allowing it to progress on the affected leaf, they pick it off, and then it just begins to manifest on a new leaf. So essentially, picking off the affected leaf aided in the issues progression. Never pick off affected leaves unless it's heavily contaminated with bugs, molds of fungus.

Thrips marks. Zoom in the picture, you can see little tiny black dots near the marks, it’s their poo, they eat and shit at the place.

I think over watering