How to tell which one

So I'm going to ask in hopes that there is a way to determine which one of my babies is doing it, but if I have to take them all to the vet, so be it. Last night I found a puddle of pee on the floor that looked bloody. It was small so we assumed it was a cat. I've got five of them. One of them is notorious for peeing where she shouldn't but I've never seen blood in her urine before (and I clean it up often enough I should have noticed it). I've never noticed blood in any of the pee in the boxes either but it's clumping litter so I don't know that I would. Anyway so I worried all night and figured I'd call the vet to see if they all need to go in or if there is a way to figure out who did it. I went out to the kitchen this morning and there was another puddle of pee with blood in it but it was definitely dog pee (she pooped on the floor next to it, her signature). Now I don't know if it's a cat or the dog. A cat could have peed on the floor and then the dog could have peed over it but I don't know, or it could be the dog. My mother-in-law said she thought our dog drank too much water and that we should mention it the next time we took her to the vet. Does anyone have any idea on how to tell who is doing it other than catching them in the act? Are there any other symptoms that would go along with this problem for us to look for? I'm trying to avoid taking all six animals to the vet but if they all need to go, they all need to go.

Is there any way for you to separate them all? Also, if you can follow the dog next time it's outside to potty and watch to see if you can spot any blood. Wish I were more help. Hope you can figure it out with out having to vet all 6.

So the vet advised to try and separate them, at least to two in a room, so that we would only have to bring two of them in. We'll try that. They didn't seem too concerned about it and just said to try and figure out which one it is. I just hope that we can figure it out soon. I don't want one of them hurting for any period of time. I tried looking at the spot where the dog peed this morning and I didn't see anything reddish in her pee but it snowed 5 inches last night so it was more of a deep puddle than a wide puddle. I get so nervous when one of my babies is sick!

I do too and while blood in the urine isn't always an urgent issue it can lead to litterbox problems. If it's an infection ot UTI which is usually the case with bloody urine it means that it's probably painful for the animal to uninate. Good luck finding the right animal.