Early molt?

Hello all, I have two 10-11 week old wheaten marans. 1 is losing some feathers on her chest and her head is looking a little scruffy. She is smaller than the other one with a slower growth rate. She seems healthy. No weird looking poops or strange breathing habits. Eating, drinking and acting normal. I’m stumped as to what it could be and why it’s only one? Is it possible that she is having an early molt? Please help! Thank you :)