I need some advice and suggestions!
About one month ago, I woke up to find my Red Factor male canary dead at the bottom of the cage. I was heartbroken! I only have a small number of small birds - less than ten each of canaries and finches, and two Ringneck Doves - in our TV room, so I do not have a lot of birds and he was an amazingly beautiful and special former showbird! He was living with a Red Factor female, so I took her to the vet immediately! We treated her for ten days with Baytril and Fluconazole, although my avian vet said she appeared healthy. She and my other four canaries are well and happy (knock wood!).
Yesterday evening, I came home at 5:00 and checked the small bird room. Everyone was fine. At about 7:30, I found one of my Societies on the bottom of the cage, panting. I believe she was a female, and she had been mating with a male Indian Silverbill for about a week, so my first thought was that she was eggbound. I took her out of the cage and inspected her vent area, and gently felt it to see if I could feel an egg. I could not. I immediately gave her one drop of Calciboost in her beak, and put her in a small box with some water and millet and a soft towel for her to sit on. I put it near a heat source, but checked every ten minutes to make sure she was not too warm. By 9:30 she was dead.

I immediately again checked her vent area, to see if I could see any signs of her being eggbound. She absolutely did not appear to be to me. I had read here last night while she was sick about "panting" finches, and I do not believe she had air sac mites as she had no other symptoms. I have no idea what happened to her!
She looked so uncomfortable, and I am now scared to death that whatever killed her might be "going around" ths bird room.
I called my avian vet to get some advice, and unfortunately (for us, not him!), he is out of town until Monday. So I am here to ask for all the advice I can get:
What should I do to help protect my bird room now? I do not have a TON of antibiotics or nutritional suppliments on hand, although I do have a few. We just finished a round of Apple Cider Vinegar in the water for ten days, followed by ten days of probiotics in the water. I add 10 drops per gallon of water of GSE to the birds' water on a daily basis, and from time to time mix that up with 1/2 teaspoon Vanodine instead. The finches eat Zupreem Natural Diet pellets on a daily basis, with a breakfast of cous cous, veggies, quinoa and soaked and sprouted seeds every day. They have dry egg food available at all times, as well as cuttlebone and Herb Salad mix. I add a couple drops of red palm oil to their wet food about 3 or 4 times a week, and about 1 or 2 times a week a sprinkle of both spirulina and Nekton-bio. Because they eat pellets as their main diet, I do not provide additional vitamins (just the Nekton-bio a couple times a week). They get about 14 hours of full-spectrum light every day, and are offered (and generally take!) a bath every day. I give them a treat of millet about once a week.
What can I/should I be doing differently, and what can I/should I do now, after Speed Racer's (named by my husband, not me!) death, to help protect and ensure the health of my current flock?
I thank you all in advance for reading this, and for any advice or suggestions you can offer!
Best!