CHICK thats not feeling well

At 3 weeks if a chick was hunched and lethargic, I would probably go ahead and treat the ones that age with Corid/amprollium in the water for 5-7 days in case of coccidiosis. Even though you are feeding medicated feed it doesn’t prevent them from getting coccidiosis. Stop the NutriDrench until finished with Corid if you choose to use it.