Is developing too fast bad for chicks

[Reaperprincess]

I don't know if I am at the right category but I recently bought afew month old chicks but when I got them they looked at least 2 months old but when i asked the breeder asured me they were only a month old.
They are rir and austrolop mix.
So am i just lucky that they are devoloped so much or can it be unhealthy for them in the long run

 

[500Chickens]

They look right for being that age. I think Australorps are considered a large breed (someone correct me if i'm wrong) so they would be naturally bigger. Here is a picture of one of my birds at 1 month for comparison to your birds. She is smaller because her breed is small.

 

[Reaperprincess]

They look right for being that age. I think Australorps are considered a large breed (someone correct me if i'm wrong) so they would be naturally bigger. Here is a picture of one of my birds at 1 month for comparison to your birds. She is smaller because her breed is small.View attachment 4124690

Thank you none of my chicks i hatched looked like that at a month so i was a little worrried