JAX
Hi Jax,
Glad to hear that your girl is doing better.
Scatt, and ( Iverlux and S76 same thing basically will get rid of the airsac mites).
Scatt, goes directly on the skin on back of neck (one drop) to be repeated after 21 days, total of twice. S76 and or Iverlux go into the bird's drinking water as per instructions.
As to the antibiotics, I would follow your avian Vet's instructions.
Regarding diet:
I feed a good quality Finch seed mix, equally mixed with good quality Canary seed mix, and spray millet.
As to veggies, I feed a great variety of greens and veggies (my birds eat better than me) which some people shake their heads at.
Romain, broccoli, cucumbers, kale, mixed spring greens, grated carrots, red swiss chard, beet greens, carrot tops, dandilion greens and chick weed in Spring and Summer, spinach (in moderation) grated beets (in moderation), peas, parsly, corn on the cob (or frozen and thawed and warmed up a bit), etc.
When it comes to fruits, Gouldians are not too keen on them, but you could try a slice of orange cut across, which my Gouldians guys seem to enjoy.
Now I am feeding around a 100 birds, so I buy a lot of greens and veggies. You don't need to rush out and buy everything on this list, lol. I would start with a small container of mixed Spring greens, wash it very well, chop some up and see what she likes. If she's not used to any veggies, she may be reluctant to try, but don't give up, eventually she will try, maybe sprinkle some crumbled spray millet on the mixture to tempt her.
I would also introduce some hard boiled egg into her diet 2 times a week. It is a wonderful source of protein (which seed diets alone do not supply), and vit D and many other healthy nutrients). The shells can be crushed and offered as well for calcium, along with a nice oyster shell or mineral grit.
I would also recommend cuttle bone, a mineral block, and an iodine block for her cage.
Good luck, and I honestly don't have that much expertise, just things I have learned over years, on this Forum, and by trial and error....

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Here are some of my guys enjoying the salad bar....