I have a RIR baby that I got at about 1 day old and is now about 4 weeks old. Unsure of the sex, we call it Jellybean. At first, Jellybean seemed to be growing right along with the rest. Then, after about the first week, it just stopped. It's otherwise healthy acting; eats and drinks and gets around fine. It started to feather out at one point and then stopped that also. I took it out of the side of the brooder that had the first group of chicks that I bought, because they were all outgrowing it. I put it in the other side with some I bought a couple of weeks later that were younger and closer in size to it. Now, those babies are outgrowing it.
The RIR baby in the back is the same age, 4 weeks, as my failure to thrive baby. These are 4 and 5 week old babies.
You can see the NH Red baby that is about 2 weeks old in front of Jellybean. The NH Red is outgrowning it, also. Jellybean still hasn't developed tail feathers.
I'm at the point where I'm already looking for a bird cage, because I don't think Jellybean will ever grow up and be outside like a regular chicken. Does anyone have any idea what's going on here?
Any advice?
The RIR baby in the back is the same age, 4 weeks, as my failure to thrive baby. These are 4 and 5 week old babies.

You can see the NH Red baby that is about 2 weeks old in front of Jellybean. The NH Red is outgrowning it, also. Jellybean still hasn't developed tail feathers.

I'm at the point where I'm already looking for a bird cage, because I don't think Jellybean will ever grow up and be outside like a regular chicken. Does anyone have any idea what's going on here?
Any advice?