Slow growing month old chick with no feathers on her head

[Georgiaclark14]

Hi, I'm a first time chicken mum to two, 5 week old chicks. Agatha is half the size of her sister, has had glaucoma since birth and looks bald as she has still has down on her head. Just wondering if anyone can give me some advice or at least reassurance that shes okay? She eats, drinks and poops fine and is full of energy. I've tried to research what's going on with her but I've had no luck at all! I'll attach some pictures of her and her sister for reference. They still sleep indoors with a lamp at night as it's still pretty cold on the evenings. Thanks in advanced!

 

[Chick-N-Fun]

She is just taking longer to feather in. What are you Feeding your flock? Feathers take protein to grow. I suggest an all flock feed or grower. Limit treats.
Best wishes and be well!

 

[Georgiaclark14]

They're currently still on chick crumb as were waiting for our order of chicke grower to arrive. We haven't really started with treats yet as we're not sure what's best for them especially protein. We have been given oyster shells and grit but I know that's for calcium. Thanks you too