There is no longer medicine in the feed. It’s a preventative, but not a real medicine (I cannot remember when that changed, but it’s been a while).
If one has it, treat everyone.
The following is long, but thorough. From casportpony.

When treating coccidisosis in my own birds I use the severe outbreak dose (0.024%) for 5 days, then the 0.006% amount for 7-14 days.
Liquid dose:
2 teaspoons per gallon for five days, then 1/2 teaspoon for 7-14 days.
Powder dose:
1.5...