After all the trouble, I recommend you very much to give all the chickens that survived,some high quality,foods rich in protein and vitamins, like boiled crushed eggs, or some cod liver canned or fresh, or some dry cat food and add some electrolytes in the drinking water, and you can also add...
If you can't find a veterinarian dewormer, you could do what I have done here successful and use a human dewormer. I have used mebendazole or in its generic name- Vermox
Reed this link
http://www.rxlist.com/vermox-drug.htm
The dosage is 30mg/kg buddy Weight and another time after 10 dayes.
Good...