So sorry about your chick. I really wish there was an easy fail proof solution to this problem, but that I know of there isn’t. I believe the OPs chick was put down because it wasn’t gaining weight due to this deformity. You might find the link in my first reply helpful, it’s another chick that had this problem that the owner got it an experimental surgery to try to correct it. Supposedly it did survive after the surgery but that owner never posted an update after that.
I wish there was some kind of research or something into this problem because it seems to be relatively common. Do you have access to a vet?