Turn them sideways, slide them in (they should still be a tightish fit) and then turn up the right way. If you have already filled them, put your hand across the top while you turn it sideways. There is no point in them being loose or the birds would have them out and everything spilt in no time.
We are not Vets, Avian or otherwise. If you have any serious doubts about your budgies' health an appointment with an Avian vet should always be your first point of call.