https://www.backyardchickens.com/threads/one-hen-eating-anothers-egg-before-we-can-get-it.1303549/Another thought is, you haven't seen any evidence of broken eggs or anything correct? Egg eating is also a possibility,
How long since the probiotic and worming?
Are you sure the feed is fresh?
Look at mfg date on nutrition tag or sew strip on bottom of bag.
Where did you get birds?
Are you positive of their age?
Some birds are 'lemons'...
....and like Blooie sez: "they ain't pez dispensers".
Just some thoughts.