Hi Shirlie,
The best thing to do when a bird is sick is to take it to an Avian Vet. Even if it dies, the Vet can do tests to determine the cause. When you continue to lose birds, then the question of husbandry will come up. What is their main diet? How often do you clean and disinfect the cages? What is the mean temperature? How often is the water changed? How often are the dishes, perches, toys, etc. cleaned and disinfected?
Dosing birds for what might happen is not always a good practice. Generally treatment upon diagnosis is better. Some treatments and supplements can build up in the bird’s system. It is possible to over supplement a bird. Some vitamins are toxic even if just a small amount over the recommended dose. Vitamin A can be extremely toxic. Air sac mites are believed to be found in most Gouldian finches and a symbiotic relationship is suspected. They mostly succumb to these mites during molt, stress, extreme temperatures or if they have poor nutrition. Preventative treatment needs to be administered at the right time, and not year round. The treatment itself can be toxic. Your best options are to consult with an Avian Vet and to try to find a reputable and successful Gouldian breeder for advice. Be cautious of advice from a breeder or pet shop that comes with selling a product. There are a lot of unnecessary products for birds, and while some are harmless, others are not. Hopefully with some help from the experts, you can determine the problem.
Thank you for asking Lafeber,
Brenda