You're correct, and have nothing to worry about in terms of the urine you are seeing. Guinea pig urine tends to be milky white-ish, so you're fine there
As for the "messy poop", I would pay some attention. The feces are supposed to be firm and pelleted, and signs of liquid-y fecal matter can point in the direction of diahrrea, which is not comfy. What vegetables are you feeding? Often times this can be avoided by steering away from water heavy vegetables such as iceburg lettuce. Also, how young are the pups? Alfalfa hay should be fed for babies up to 3 months, then switch to timothy hay (I apologize if this information is already known, just making sure I cover all the bases).
So, check the veggie intake, and see what happens. If you're not comfortable of course, see a vet