Australorp laying shell-less eggs

My first experience with an Australorp. Such a lovely, sweet bird. She began laying June 4, at exactly 20 weeks of age. We were away the next few weeks so I'm not sure how things went from there. But since I've been back, she has laid two shell-less eggs in the past week, dropping them from the sleeping roost. She has not, to my knowledge been in the nesting box at all during that time so I think she has only laid one "real" egg since I returned two weeks ago.

I'm providing plenty of oyster shell. The grit and oyster shell are being consumed at an unprecedented rate by someone - I'm not sure if it is her or someone else, but for a flock of five I'm going through four or five times the amount of it as I have in the past. Not sure what's up with that.

She seems perky and active and interested in food so I don't think she is ill. But should I be worried? I wrote off the first shell-less egg as an anomaly, but another one a few days later begins to look like a pattern...

 

Hi @oldhenlikesdogs She is by far the calmest of the flock so I don't think it's stress. The coop is pretty much Fort Knoxed at night plus gated area around it, but of course, who knows what lurks in the shadows. I hope everything gets into synch for her soon.