i just want to chime in here: while OP's snakes are obviously dealing with some sort of issue, sometimes when a snake sheds, the skin pulling away from the cloaca causes it to get irritated and possibly bleed a bit. it's not too common, but it does happen; it's happened with my oldest male once before. that's likely where the blood came from.
still, diarrhea is not something to take lightly IMO.