From my own experience I can say that this claim has been and still is true with my birds over 20+ years.
Cold stress or any other stress the hens are exposed to leads to more male offspring.
:hugs I am sorry this happened, but you did the right thing.
In my view the chicks are still much to small to receive this kind of "educational" pecks and even less from a rooster.
I once dispatched a gorgeous BCM rooster for suddenly attacking a broody hen through the fence as she took a...
Calcium 600 citrate +vitamin D administered every evening for 7-10 consecutive days can help with building good eggshells.
If she does not improve, you might start her on antibiotics as broken eggs inside the oviduct will cause infection.
I have observed this for 20+ years with my hens, no matter the breed or mix.
Here is some more scientific findings on the matter:
"effect of age on the yolk to albumen ratio in chicken eggs" https://pubmed.ncbi.nlm.nih.gov/8464799/
We do find our French Marans eggs to be the best, followed up...
Yes, there is a difference in the yolk to albumen ratio depending on the age of the hen (yolks get bigger as the hens get older) and the variety, as bantam egg yolk to albumen is better, meaning more yolk as in standard sized breeds.
We also notice a difference in breeds and in individuals and...
I have several hens that will kick out any kind of fake eggs: wooden, porcellain, plastic with or without sand filling, golf ball, plaster, you name it.
But strangely, they would tolerate boiled eggs for a while.