Speckling can show up when the brown coat isn't applied evenly
It may be more common in darker brown eggs, but it can happen with regular color ranges as well.
My Rhode Island Red used to lay what I would consider a classic brown egg, but then her ink printer must have run low and it got speckled.
Meanwhile, my Barred Plymouth Rock lays the lightest creamy egg of my whole flock, with just a few tan speckles on the end. So weird.
Unrelated
Maybe it's the angle of the picture, but some of your eggs might be pointy-side-up?