Yes. The issue may be that their immunity is compromised, or the environment where they are is heavily contaminated with cocci. I've never had to deal with this issue myself. Are you positive that they have or have had coccidiosis? The Amprolium in the medicated feed is a thiamine blocker. Without thiamine, the organism can't replicate. So, in theory, it keeps the load down while the chick builds immunity to the organism. But, if their systems are compromised by stress, crowding, illness, or any other issues, their gut flora will not be balanced, and the bad guys will take over. If you have wet land in your run, drying it out would be your first step in ensuring the health of your flock. I'm not sure what is in the Corid, but, would not want my birds on it any more than necessary, b/c that will mess with their gut flora. I've never used medicated feed, nor have I ever had to treat coccidiosis.