Was I hoodwinked? Small chicks

[Frogorf]

Hi New Friends! I have a question. I'm one year in on keeping chickens, so yeah. Really novice. Anyways...

I bought some chicks on May 5. Hatch date was April 30th. 3 brown Sussex and 1 Plymouth Rock.
Yesterday I bought 3 Barred Rocks. Hatched April 26 th. Totally feathered out and healthy all the same size. but when I look at them in comparison to my other chicks...They're half the size!! Course I didn't see the difference until I was home. So I contacted said breeder just to verify that, they weren't Bantams. She assured me they weren't. Are they going to die on me ( failure to thrive?) Or am I overreacting? Is it possible for younger chicks to " feather out" sooner if they're kept colder? They're other wise healthy chicks.
My Roo is a Buff Brahma so I am concerned if they turn out to be bantams or just runts

Cheers

 

[Fluffnut]

Can you post some pictures?

 

[Nats Chickens]

Pics pls!

 

[Frogorf]

My bad, I should've taken pics. Will do so in the Am..

 

[Compost King]

Since they grew up in different environments it could be an environmental issue. Possibly the larger ones had higher protein feed. Could be all sorts of variables and pictures in the AM will help people figure it out.

 

[Frogorf]

Ok. Here’s the pics. I am practicing bio security, so they aren’t side by side comparisons. Then Nalgene bottles are the same size, just different colours.
The bigger velociraptors are my original 4.
And yes I know my Plymouth Rock has a weepy eye. Just a scratch.

I am not a photographer by any means. Hope these pics are decent

 

[Harmony Fowl]

They seem awfully close to me. It looks like they all would clear the top of the bottle by a little if they were standing up straight. Comparing apples to apples as much as possible, your first barred rock is also a boy, while your new ones are all female. That could also account for some difference.

 

[Frazzemrat1]

It could also be hatch date inaccuracy, I'm not sure. the cockerels in the first two pics look perhaps a little younger, but I wouldn't say much.

 

[Ol Grey Mare]

The first pic shows a br cockerel, which can account for some size difference.
Pullets all appear healthy and developing.

 

[Frogorf]

Yeah I thought Betty Boop ( BR) may end up being a Dwayne the Rock Johnson. The one Sussex by the bottle with the BR is a pullet I thought. If you compare her to the Sussex cockerel in there as well. He's not in the frame. ( sex my chicks! Category coming up! )
So possible hatch date inaccuracies? I'll go with that.
Once quarantine is over I'll add some pics of them together. Minus 1-2 cockerels