Who's laying the dark brown egg that keeps getting darker??

[Hopps]

Its been a fun adventure! maybe, just maybe the leghorn laid 2 eggs in one day. Its very rare but if any breed can do that its a Leghorn.

Yes definitely a fun adventure! I do think it was the leghorn laying doubles. It was two small white eggs instead of her usual relatively large eggs!

 

[Vanilla Gorilla]

Is it possible that my Brown Leghorn is a Welsummer..? Here's a picture of my brown leghorn. But it doesn't make sense because sometimes we pick up 2 white eggs at a time.

That's exactly what I was going to say. That looks exactly like the egg my Welsummer lays. Check earlobe color. Red means Welsummer, white means Leghorn. Good luck!