I had an extreme frizzle silkie runt, she was so extreme, that at 10+ week old she was the same size as the 6 week olds she was sold with. Now 4 weeks later, the 6 week olds have outgrown her. She has a voracious appetite and has started to put on weight, but is not as active as the rest (at first she barely moved at all). I was worried whether she would make it at first, but she definitely has the fight to live and seems to be doing fine for now, she may never fully be an outdoor chicken, but I think I'm okay with bringing her inside from time to time.
Honestly, yours looks fine, just smaller, but overall healthy and active.
Honestly, yours looks fine, just smaller, but overall healthy and active.