Ok, listless with diarrhea....depends on the diarrhea. Is there blood in the stool at all?
You could have an ecoli issue or a coccidiosis issue. Depending on which depends on the medication.
Ecoli can be treated with the Tetracycline or Terramycin (Oxytetracycline)
Coccidiosis needs sulmet (sulfamethazine sodium) medication
But, if your feed is already medicated, you don't want to dose with the sulmet. Medicated feed already has medication to help with coccidiosis.
If you are having either of these issues, you need to change the bedding, clean the coop, clean all the feeders and waterers. Coccidiosis can be "killed" with ammonia. Ecoli with bleach solution.
I would also boost the birds with some polysol vitamins, yogurt(plain) and scrambled eggs. You can also offer water with elecrtolytes, briefly. Or some people put apple cider vinegar in the water.
Take out everything but the layer pellets until you have a handle on the diarrhea. That way you can be sure the birds are eating a blanced ration and not just "treats".
