All my Budgies, Cockatiels, Conures, Gouldian Finches, Topknot Doves, Pigeons, Moustache Parrot, Princess Parrot, Bleeding Heart Dove, Jap Quail, King Quail, Masked Parrots, Peachface etc. all survive on Trill Budgerigar 10 kg mix. It contains shell grit as well. The indoor budgies get the same mix. I supplement this with pears, (they love them) and oranges sliced in half. Some are as old as 10 years and still doing fine.
In regards to sunflower, use only striped sunflower, not the black. The black has too high a fat content and can prove fatal with excessive use.