I have two Parakeets. I purchase seeds from Dr. Foster and Smith which is mixed. I also purchase separate seed which you can add to your parakeets' diet: red millet; sunflower seed; safflower seed, hulled oats,cracked corn, etc. I mix them in with their daily diet.
I also create food for them: bread; eggs; lettuce;corn, frozen vegetables, etc.
I put this on top of their food to add nutrition. They only have 24 hours to eat this food.
Whatever is not eaten within 24 hours, I throw away.
They eat the food I create, the mixed seed (sometimes they share food with other birds as you see on the packages).
I purchase treats to give them an additive once in awhile.
Both are doing fine.