If my memory serves me right the pair of budgies I had in Massachusetts moved to New York with my family, and when we left New York for California I gave the birds away to a friend. That would make these two budgies eight years old when I gave them away, and they were very active, very noisy!
Birds do get ill, often with a form of an avian virus, a flu, so only a veterinarian who cares for birds could diagnose what is wrong with your birds if their problem is a bird flu.
Is it possible that your budgies are bored with their cage?
Do you allow them to fly around, inside of your house for exercise?
Birds are like other creatures in that they do need to have exercise as a part of their lives in order to be healthy, and a good diet too in order to remain both happy and healthy.
Have you looked up what kinds of vegetables you could give to them to stimulate their appetite and interest in their lives?
Perhaps someone who has birds now, can give you a better idea of what budgies like to eat outside of the birdseed that you buy at the store.
Another possibility to look into is the birdseed you are feeding your birds.
Is the birdseed stored in a dry environment where mold and fungus will NOT grow on it. Fungus growing on birdseed will make budgies ill if this seed is fed to them.
Do you give your birds’ fresh water every day?
Do your birds have a cuttlebone to sharpen their beaks?
Are the perches in the cage kept clean?
Do you change the paper on the bottom of the cage as soon as it is soiled?
As I remember, budgies soil their cages very fast!
Bad bacteria grows on budgie doo if the doo is left in the cage.
Good luck in solving this problem.