When we have a sick chicken we take her inside and pamper her, its worked like magic so far. (Penny had an impacted crop; we massaged it every few hours, etc.) That way they're warm and not getting picked on either. But I agree, cedar is bad bad BAD! I'm really sorry for your losses, our Barred is the sweetest thing. I would switch to pine, immediatly, but make sure there's no leftover cedar dust because that could probabaly make them sick too. I hope your other birds get better!!! And welcome to BYC!
We learn from our mistakes!