Blueside, I think I would probably treat the flock with a 5 day course of Corid in their water. That looks like possible coccidiosis to me. Dosage is 2 tsp of Corid liquid or 1.5 tsp of Corid Powder per gallon of water for 5-7 days as the only water source. You can find Corid in the cattle medicine aise of the feed stores. It is sometimes sold as Ampromed or Amprol. Sometimes capillaria worms can cause blood in droppings, but I would treat for coccidia or get a fecal sample looked at by your vet.