Not comparing across breeds. The same age chick he is pictured with is a female Australorp. Also he stopped growing before the leg problems which I am pretty sure was caused from a leg injury due to trampling from his hatch mates. They were double his size before I removed him and a few more normal runts from the main group. I'm really more curious wether anyone has had a chick as drastically stunted before and if so did they catch up ever or stay on the smaller side. I mean he doesn't look like he has it in him to get up to 8 lbs.
It could just be that when he had his leg issues, there was an associated vitamin deficiency, and that period of time caused him to be weakened and not grow as vigorous, so now he is just catching up. Also right now I have a mixed breed flock and my Australorp is on the slower side to grow and develop feathers. You really can't compare across breeds. Each chicken breed has its own rate of development.