Maybe my monitors are brighter than yours. The first one has actual polka dots where you just hit it with a black brush with a click of the mouse and so it left black dots in a couple places.
2nd one is OK but obvious, it doesnt look natural at all.
3rd one is really bad below the fish
6 and 7 arent that bad, but there are dark areas then just the normal blue blurred background, with a couple strokes between them.
Anyway, maybe it's my LCD. I havent calibrated it ever, it's just on stock factory settings.