in my siggy link is a ton of health info, scroll down to the worms and lice section. There are links explaining about the different worms, and how to treat; also in the section titled "medication charts" or something along that line there are more dosing instructions. Make sure you do the doses for banties!
Do you free range? If they are primarily cooped you may not need to, but if they range in the yard they may need it. They get worms from other wild birds, and from eating bugs. The worm eggs are in the bugs that they eat, gross but that's how they get the worms.