Since you've gotten no replies and I don't know budgies, my suggestion is that you might phone an avian vet to ask advice. It surely can't hurt, though Monday morning would be the earliest that would be possible. If you need contact information for vets I know who do phone consultations, I can PM some recommendations to you.
Before making that call, read at this site:
http://www.exoticpetvet.net/avian/budgietiel.html About 1/3 way down the page, crusty beak is covered under
Parasitic Disease.
I hope this is helpful and your birds are soon healthy.
Paca