Runner ducks missing feathers pic included

[crazybirdlady99]

I have 8 runner ducks that hatched on May 18th. Four of them are missing the feathers on their wings for some reason. It's been like that since they were little but I thought they would come in with the rest of the feathers.

I feed them 18% check starter crumbles supplemented with brewers yeast.

Any ideas on what could be causing this?

Thank you!!!

 

[Poultry parent]

i don't know if this is what it is but ducks 8-12 weeks old molt out their feathers and grow adult feathers in