Chick not growing

[Corrisionworrision]

I got 2 susex and 2 easters from TS, all of them are about 2 weeks now and one of the susex is barely growing, she's very tiny and almost has no feathers, left photo is her next to her sister and the right photo is her on the left next to everyone. She's barely eating and looks a little lethargic, could she be sick or could it be failure to thrive? And if she's sick could it be contagious?

 

[sourland]

Any chance it's a bantam?

 

[Corrisionworrision]

Maybe?? But she was the same size as the rest when I first got them and wouldn't she have feathers even if she was a bantam?

 

[rosemarythyme]

The lethargy is more concerning. Have they had any outside exposure or have they been in an inside brooder the whole time? FTT is probably more likely here given the lethargy and lack of interest in food.