It is correct that you need to change the seed because the budgies will often drop the empty seed hulls into the bowl on top of their good seed. Budgies shouldn't live on a seed only diet anyway as it's not good for them. It's recommended they have 1-2 teaspoons of a good quality seed mix per bird, per day (you could divide that into a morning feed and an afternoon feed). On top of this they should have 24 hour access to good quality pellets (a lot of budgies like the Zupreem fruity pellets in canary size), and also access to fresh vegetables (be sure to check out the diet section of the forum as some vegetables are not recommended or even harmful to birds). You can offer them a little bit of millet as a treat as well, but not as an every day thing.
It may take some time for one or both birds to start eating some foods, but don't give up.
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