Cyst on the wing

[Bosque]

Two of my birds have a cyst or bump on thier wing close to their body. They were born on July 19. What is it? Do I need to medicate it or is it something to do with their feathers coming in?
Thank you,

 

[NotTheMomma]

Could just be an air sac. Can you get a pic? Is it red or painful? Do any of your others have it? Chick breathing ok? Do a search for air sacs in chickens, and see if it's in the same place. Most likely it's nothing to worry about.

 

[Bosque]

I cannot figure out how to post a picture. Is there a link to add photos?
Reading about air sacs seem to indicate e coli. I change the paper towl over the wood chips twice per day. Sometimes, I do see the chicks standing or sleeping on the food. Also, just three days ago I ran out of food so I bought medicated feed from Wally World. Could that have something to do with it. Should I dump the food? I only have three chicks in a large plastic tub, but two have it all of a sudden. One has one on each side.