Causes for Blood in a Puppy's Stool?

I have 5 very energetic puppies (Siberian Husky). One of my pups suddenly lost his energy and his appetite. He was only drinking water (a lot). I gave him chicken, etc., but he still didn't eat. I drove him to a vet. The vet said we needed to examine the stool of all 5 puppies. For the other 4 pups they found nothing in their poops, but the one who was ill had blood in his stool. The doctor also found out he has a protozoan infection.

I was starting to cry because I was also suspecting it might be the parvo virus. I was thinking that I might lose him. I decided to admit him and let them give him an IV fluid. It could be the parasite that makes my puppy have poop with blood. The vet advised me to give my 4 puppies an immunization and an anti-diarrheal antibiotic to insure they're healthy, because they've been exposed to the ill one.

Later that night I observed that they had slightly soft or loose poop, but they are still eating a lot and drinking a lot and are very energetic too. Can I ask for some any advice guys? This is so stressful. I only have had 3 hrs of sleep.

Thank you.