If you know you have worms you can treat each bird with ivermectin pour-on cattle wormer. It is time consuming, but it is also effective.
However, if you have never wormed them it's best to start with something like Wazine, it's a liquid treatment that you put in the water. Follow directions on bottle. 4-6 weeks later you can re-treat with the ivermectin pour-on.
You can also use Safeguard (fenbendazole) paste disolved in the water, it is also effective. However, you will need to use the Wazine first if you have never wormed. I don't remember the dosage for Safeguard but I believe it is a 2" strip in 1 gallon of water. You can search on here for the exact doseage (probably in either the turkey or peafowl forums).
As for what to feed for them to be their healthiest? A good quality egg-layer feed for birds over 16 weeks or a good-quality chick starter/grower for birds under 16 weeks. You can supplement with 'treats' if you want.