It would help if you can post a picture of the poop.
Sometimes they can expel some intestinal lining, but if it is in fact blood then it may be coccidiosis and you would need to start a treatment of Corid with the active ingredient amprolium as soon as possible. The poo may be normal if they have drank a lot of water but could indicate something else or worms.
Problematic poop is problematic if it persists over several days. According to what the chickens eat, how hot it is, how much water they drink, poop may be runny once in a while.
If you suspect worms, and there are other signs of worm infestation such as bedraggled feathers, and lethargic behavior, I urge you not to worm until you have their poop tested for parasites. In fact, having the poop tested will tell you if they have cocci, too, although a round of Corid isn't all that hard on chickens. But worming when no worms are present is not necessary. A vet can test it for you or send samples to your local agricultural lab.