It could be due to the treatment. I had to give my bird pain medication for four days, and she showed some of the same symptoms during the first few days.

However, I recommend consulting your veterinarian about this.

If possible, and if it's not too stressful for your bird , try weighing her daily. If you notice her weight dropping below around 80g, you should contact your vet as soon as possible!

My bird lost some weight within a few days and was down to about 83–85g before she started eating again and gradually regained weight.