OK. Just thinking.
Your original question was could it possibly be worms, if you haven't wormed them it is still a possibility.
You could worm them with Valbazen 1/2 ml orally and then repeated in 10 days for each chicken or Fenbendazole (Safeguard, Panacur) at 1/4 ml per pound for 5 days in a row. There is a 14day egg withdrawal (throw away period) when using either of these wormers.
http://www.the-chicken-chick.com/2015/11/control-treatment-of-worms-in-chickens.html
