Contrasting Egg Sizes

I have two batches of Barred Rock chickens, from two different hatcheries.  One bunch hatched in early May, so they were coming into maturity (insofar as egg-laying capability goes) after the fall equinox when days were getting relatively short--and declining.  They didn't start laying until after the winter solstice, at about eight months of age.  The second group was hatched in late September, so they hit maturity after the winter equinox when day length was increasing.  I started getting my first eggs from them at five months.

I realize that, despite the nominal breed being the same, the two groups of birds might be different in important ways.  However, the age gap is interesting, as is this:

The one on the right is from the second group, while the others are from the older chickens.  The bunch that waited eight months before beginning to lay eggs has laid full-sized ones from Day 1.  They have all been about 52-64 grams, or large to extra large.  The one on the right is 37 grams, aka peewee-sized (which is not uncommon for young birds just beginning to lay). Hopefully they increase in size soon.