BC marans eggs ever dark on top with lighter bottom?

[TinyBirds]

Since I'm new to dark-color eggs, is it normal to have received eggs that are darker on one end than the other? That's how all the eggs are. It definitely doesn't look like anyone tried to paint them or anything (and the lady was really nice), but I just haven't seen eggs that are different colors on different ends of the egg before. Is that sometimes normal for dark eggs? It almost looks like they were in a nest with the bottom of them getting lighter from facing downward for some reason. The part that is darker is the part that would be showing if you see them sitting in a nest. I can't tell why they're like that. All the welsummer eggs I received are more of a solid-brown instead of faded 2-toned. Thanks for your input!

 

[TinyBirds]

I just looked at them again and I guess the welsummer eggs are similar to that also. It's just a bit more pronounced lighter-bottom w/ the marans eggs I got. If viewing them from the top in the incubator, they all look nearly identical (maybe the marans being a tad darker), but if you lift them and look at the bottom of them all, the marans are a tad lighter on bottom. It's barely noticeable but I was just wondering if that's normal. Thanks!