I have had one of my chickens laying our first ever eggs. She is a white leghorn and started laying at 16 weeks. 4 of her 7 eggs have been rubber shelled, there is no hard shell at all. 3 of which she layed from the roost. The 3 hard ones she layed in a nest box. Then this morning I found another egg under the roost with a soft shell. It can't be from my first leghorn as she layed a hard shell egg at 3pm yesterday. I think it's the first egg of the other leghorn (she has been squatting for 2 weeks). What am I doing wrong. They are on a good quality grower feed (I have young chicks not laying too) and I have oyster shell available at all times. I also crush egg shells which they love and give them a high calcium probiotic yogurt ever 3 days. What else could I try? Or is this because they are laying too young?