How old are your chickens and how are they acting? If you see any young birds with lethargy, hunched or puffed up posture, not able to eat, or runny poops, those are signs. You could call your vet to ask if they will let you bring in a ziploc bag of some droppings to check with a fecal float test for worms and coccidiosis. It is difficult to diagnose coccidiosis with a poop picture. Some strains of coccidiosis may cause some blood, but others do not. If in doubt, Corid (amprollium) can be used as treatment.