Small pic, but looks like roundworms. I suggest worming with wazine. If one has, all likely have, so treat your whole flock. If you have egg-producing hens, you'll need to throw eggs away for 14 days. Make sure to do two treatments to get adults and then the eggs that have hatched. Dosing info:
CHICKENS - 4 to 6 weeks of age: for each 100 birds, use 1 fluid ounce (30 ml) of Wazine-17 in 1 U.S. gallon (3.8 liters) of drinking water.
Over 6 weeks of age: for each 100 birds, use 2 fluid ounces (60 ml) of Wazine-17 in 2 U.S. gallons (7.6 liters) of drinking water.
1 liquid ounce = 30ml = 2 tablespoons