New baby budgie

You did right. If male or female start attacking younger budgie, it is better to separate. Do not worry, when all babies grow and you stop breeding, you can join them. Just provide enough space for all of them. Good luck

Acting weird

So first and formost when in doubt see a vet. Budgies hide any signs of sickness or issues they may have like professional spies. You can even call the vet explains whats happening and see what they say.

That aside since I can not see or hear your bird all I can say is this. Budgies always do a little tail wag it can mean a great deal many things from excitment to upset. Budgies also make tons of different chirps, squaks, chatters and all kinds of noise. So Id have to hear it to be sure. But call a vet.