Never received from molt

[lukes52]

My ISA Brown chickens molted last fall and never regained their feathers and continue to look worse but act normal. The reds in the same coop look normal.
What is going on?

 

[nuthatched]

Diet?
Space for how many birds?
Checked for mites or lice?

 

[GlicksChicks]

Did they get extra protein to grow feathers back?

Did the reds molt as well and recover?

Could the reds be pulling and eating the feathers of the browns?