Lack of feathers on 6week Orpington

[MysteryChicken]

Chick starter

Hope not she’s my only buff

What's the protein content?

 

[Sinko_26]

Its not the chick feed the feed they are on is fine. All the other birds have fully feathered. They are seven weeks old now and she still looks rather similar.
I have put vitamins in the water now but surely this is more common and someone knows what’s up.
Hopefully no long term issues and she will feather properly after a molt but yeh strange!
these photos are today