Need some help: white eggshells found in coop but my girls lay brown????

[sunnysc]

Just came in from going to collect our eggs and found white egg shells in the bottom of their coop. I only have 3 pullets and they all lay light to medium brown eggs. There was a brown egg in their favorite box but also white eggshell in the bottom of their coop where there water & food are (small run). Just wondering if I could have an egg eater OR if the shell is from something else??? I've never seen them lay a white egg so I'm perplexed on this one. Anyone have a clue?

 

[Maggiesdad]

Color is the next to last thing added to the egg before laying. If she had a glitch, she could lay a white egg, which also could explain it being broken...