another advise please
 

I was looking at one of my plants yesterday and I noticed something that I didn't pay attention before. On the back of three of the leaves there are some white spots, excavated. I don't know what these spots are so I need your help please. I attached a couple of pictures so you can see the leaves. Not the center ones in the first pic, but the margin ones.

That's just physical damage. Don't worry about those.