I don't breed birds so may not be of much help. Do you know if you are using the same type of nest box and nesting material as was used in the past? Are you feeding the same types of foods and offering some good healthy softer foods for them to eat as well? Also some birds when reset up in a new home with new supplies will lose their first one to two clutches before getting back "into the hang of things" Sorry I'm not more help.