Hello petlovers

Lately I've been seeing blood in one of my cats stool. I have three cats, one female and two males and It is pretty hard to tell which cat it is but since my female cat doesn't cover her stool up then I know it is hers. Also it is a soft stool, is that ok when a cat has a soft stool or is that a health problem. She seems healthy, eats well and runs around with my other two cats and she has shiny fur. I just hope she is not sick, I don't want any problem especially when she is only young yet. Any help or suggestion would be appreciate. Before I rush her over to the vet, I want some answer. Does anyone had this problem with their cat? Thanks for your time and consideration. Please reply!!