I checked a gouldian box this morning looking for two overdue fledglings. I found the hen, one healthy chick, 5 eggs and a chick with splayed legs

. So at best guess the chick would be 25 days old. I know there are plenty of methods out there for trying to straighten splayed legs, but has anyone managed to do it successfully with a finch at fledgling age?
I'm not sure if it is worth trying to fix it or if I should just put it out of its misery.