Balding area by tail?

[KnightsMist]

My chicks are about 3 weeks old and all seem to have missing feathers just above their tail areas (see photos)- is tbis normal?? Should I be concerned or do anything?

 

[Aapomp831]

No they are just growing their feathers. Mine are all about 4 weeks and their back area above the tails are taking the longest to grow in.... it’s probably fine!