Thanks for the update. Hopefully the vets can help and Jambit will be back with you and causing mischief very soon!
I personally wouldn't recommend adding any supplements unless it is mentioned by an avian specialist. I also wouldn't add anything unless it is designed/made for birds. (e.g I wouldn't add human supplements to Alfie's diet).
Speaking of teas... I have started Alfie on an avian tea (from here: https://www.northernparrots.com/pollys-natural-deptpollys_natural/ ) and he seems to enjoy it. I brew it in a cup and let it cool then just let him have it straight from the cup. He seems to like it so far, but he's only had it three times. I went for the 'golden blossom' variety because the others were out of stock.