They look like some mechanical injury - scale is very regular shape. Some bug or maybe a snail or even mouse/chipmunk or another living creature may have chewed on it, but that kind of injury is almost always on edges. I have jade plant that shows teeth marks (!) in the middle of the leave - I know it was chipmunk since I saw him...Rina

I agree. Your plants look healthy. Sometimes such brown spots simply appear, maybe a leaf comes out already having a brown spot or the plant kills its own cells to avoid the spread of a fungus (My Opuntias do), but if your plants look healthy it's fine.

Thank you both. I'm very glad to hear that they look fine and no bug problem!

here is photo of "most chewed on by the chipmunk" succulent - all the marks: