It should help symptoms within a day or two. What signs are you seeing now with the others? If you have the liquid Corid give all of the chickens 2 drops of undiluted Corid orally twice a day. If you have the powder Corid mix 1.5 tsp into 10 ml of water, and that is equivalent to undiluted liquid Corid. You can also mix some of their feed with Corid medicated water to get more into them. If at any time you want to get a fecal test checked by a vet to make sure they have coccidiosis, go ahead and see a vet with some fresh droppings. They may prefer to prescribe a sulfa antibiotic, just in case the coccidiosis is resistant to Corid.