Is their water font in direct sunlight?
Has anything scared them enough to make them hit their heads on the ceiling?
Do they stagger and sit down when you pick them up and set them back down?
Have they eaten any moldy or wet feed?
Usually problems walking come from either encephalitis or nerve damage. They get nerve damage if they do not drink enough water in the course of a day. They get encephalitis from eating wet or molding feed. It is almost always nerve damage though when one cant walk right. There are a bunch of reasons why they sometimes won't drink water during the day, like being bullied off the water, not enough watering space (for a dozen birds you would want a couple linear feet of watering space), or the water is hot and they don't want to drink it.
There are some other ailments that cause them to walk funny/not stand but they are much less common than what I've mentioned above.
Nerve damage can occasionally heal but most times will lead to the bird needing to be euthanized. If they hit their heads "boinking" the ceiling they usually will heal given time, if isolated and kept warm. If encephalitis you'd need to consult a vet, but again that is very uncommon.
