Aww I am so happy for you! and that they are now best friends. You might try just plain ole organic hemp oil and see how that goes. I had to stop buying the CBD it was just too expensive. Congrats though for having a happy beautiful flock. :clap
You wouldn't happen to have any hemp oil? I give it to my one dog who has anxiety and it really helps her. Might be worth trying with your duck. I hope she can at least see the others. Isolating them isn't so good.