Okay, it's sounding more and more to me like it's a newbie thing. I'd give it a few days. I'm glad everything else has been going good with your flock!
How long has she been laying like this? I'm kinda thinking that the issue will sort itself out. She's young and has alot of time to get things figured out!
If it's only one of them, then I'd say it probably has to do with her reproductive system. My guess would be that the egg is kinda pausing in the oviduct, resulting in an extra deposit of calcium on the shell. Still nothing to worry about. Can you rub the calcium off with your nail? They're...
I've seen that the cause for a buildup of calcium is sometimes improper nutrition. Say if your hen is eating too much calcium and not enough other minerals. What all do you guys feed?