If everyone is doing fine, active and acting normal, nothing. You can make sure they're on a balanced diet and watch for any signs of lethargy or laying issues from a specific bird.
You can treat it, hopefully, with amoxicillin but you have to wait for signs of illness so you know who it is.
Provide constant access to their feed and stop all the treats. There's nothing wrong with them except they're spoiled.
Mealworms, seeds, grain, greens, fruit and vegetables are treats, and treats do not make a good diet that they will do well on.
Feed them their formulated feed and only give...