Can I feed chick feed to older chickens???

[emzee]

I have a sick 8 week old silkie chick that I am thinking about moving out to the rabbit hutch. The hutch is currently holding 2 grown silkies that are also sick. I would keep it inside longer, but it's box is getting kind of small for it and it's starting to smell worse the older it gets. Since it still needs chick feed, can I also feed that to the older silkies? (The feed is medicated.)

 

[canada-goose]

It would be okay to feed them starter but I would hesitate to throw some already stressed chickens together when they're sick. Not good.