Thanks Dawg. Okay, I hope you are not totally confused now. Just go ahead and treat with SafeGuard 1/2 ml for each chicken, start the Corid, and IF you think you may have tapeworm, then when the next dose is due in 10 days, it may be best to use Zimectrin Gold, about $9, versus Valbazen...
Since your chickens are 3 years old, I would probably go ahead and give them a dose of Safe guard (fenbendazole) and start the Corid. If you think those white specks in the poop are tapeworms as Dawg53 has pointed out, you will need to give the SafeGuard for 3 days in a row--is that right Dawg...
Welcome to BYC. The dosage of liquid Corid is 2 teaspoonful per gallon of water for 5-7 days. Change it daily, and make it the only water supply. If they are not drinking well, they will need to be given some with a dropper or syringe, or have their beaks dipped into water like a chick...