Rest in peace, indeed, precious bird. I know, I say this to everyone I meet who is experiencing a loss. It was in a sympathy card when my Mother passed, and it stuck with me. The message was... "May the pain of losing her soon be outweighed by the joy of having had her in your life." That's you, Tweety.
this happened to a group of frogs I had. They were doing so well until one passed. Within a couple hours, they were all dead. It's so devastating and it made me feel like a failure of a pet owner, I can only imagine how you must feel. Losing pets is hard, but it's the worst when you don't know why you lost them. 
