New chicks starting to do this....

[Wol1]

I thought chick feeds were "complete".

 

[Nambroth]

I thought chick feeds were "complete".

Some are.
Some are not. Note that many Major Brands have had recalls several times in the past, due to the formulation not having enough of a given vitamin, etc (You can search for Purina Recalls, for example).
Some are old. The nutritional value of foods, especially some vitamin complexes, breaks down with age. Do you know exactly when the feed was grown, milled, and bagged?
It is also important to note that some vitamin deficiencies are passed from mother hen to her offspring-- after all, she forms the egg where they start life, so if she is deficient then she can pass it on in some cases.

As you can see, deficiencies can depend on genetics (heritage from the mother stock), feed type, formulation, age of feed, etc. It is not quite so black and white.

 

[Wol1]

Thank you. I've also been thinking about it lately because I suddenly started getting a lot of thin/soft/non-existent shells. Then, just as suddenly I was gradually getting good eggs. Only change was a new bag of feed.

I'm thinking of switching to whole grains. Buying corn from someone we know and grinding it as needed. Supplementing with oyster shell and Hubbard Feeds Homestead Chick-En-Egg (while hoping that IT is fresh).