Interesting point about squash. I'll be starting a veg garden next spring and wondering what to plant for my girls. Definitely will include squash! Thanks for the tip.I have many high-production laying hens, and quite a lot of those hens are ages 4 years and up. I have seen similiar eggs as yours by the end of summer/end of their annual laying cycles. The hens molt yearly each october/november and stop laying. When they resume laying each early spring, egg shell hardness is back to normal again.
My hens are free-range, and in addition they always have access to layer pellets and oyster shell. The past 2 summers i have also offered an abundance of yellow squash and zucchini squash from the garden. Their egg shells have seemed to remain harder/firmer until molt. (No noticeable egg shell thinning yet this year.) Im beginning to suspect the extra calcium in squash may be even more beneficial to high-production layer hens than oyster shell. You could offer your girl some squash or other veggies/fruit high in calcium to see if her egg shell hardness improves. I would be curious to know your results. Either way, she should enter molt soon, which will give her body a chance to rebuild its calcium stores.