When birds upchuck seeds and vomit in a small amount its often just an upset stomach. Once the vomit is expelled from the stomach and the bird usually acts well and is bright and happy again its GOOD! If he's eating cauliflower after he was vomiting then its even a better sign.
When your bird doesn't eat, is lethargic and has no energy, doesn't sing or play, or is puffed up and sleeping often, is when you have a problem.
Keep a watch on how much he eats this weekend, don't offer anything new food wise, limit the millet and keep his diet simple for the next few days before you can get him to see a vet.
I hope he will be fine.
When your bird doesn't eat, is lethargic and has no energy, doesn't sing or play, or is puffed up and sleeping often, is when you have a problem.
Keep a watch on how much he eats this weekend, don't offer anything new food wise, limit the millet and keep his diet simple for the next few days before you can get him to see a vet.
I hope he will be fine.