Black spots in the white of a a black diamond?

[SHARK13]

Pretty much all pure BD will get this type of dirty spot eventually with age. Especially after many breedings. Some hold out longer than others, some not as severe as others but the white never comes back. So if a spot gets damaged or bitten by another fish, it will always have the black coming through from then on.

 

[Leo Messi]

Yep, pretty much all pure BDs get it. Some sooner, others later. I'd say most get it a bit later, when they are adult. But happens to - just a guess - ~90% of all BDs.