Bantam or underdeveloped?

[littlepip]

I got this chick free from a feed store who was planning on culling her due to her inability to walk. I fixed her splay legs and she ended up regaining her ability to walk/started growing after much TLC. She’s always been a very slow grower, considerably smaller than her sister from the same batch. They’re 3 months old now, and she’s still small but nearly fully developed. She has a squeaky cluck still, but her feathers are otherwise developed. Is there a possibility she’s a bantam, or is this dwarfism/FTT? She’s behaving normally and eats/drinks/poops well, but I know sometimes FTT just kicks in One day and kills them, so I’m cautious about getting my hopes up. I looked up dwarfism and she doesn’t seem to display any of those traits, so I’m conflicted. Here’s a photo for size comparison.

And about a month ago

 

[oldhenlikesdogs]

If it's the same breed as the larger one it is just undersized from having troubles when younger. Sometimes they catch up eventually and sometimes they just stay smaller.