Giardia or coccidia comes to mind.
Some puppies are really bad poopers. I would visit a vet soon if you can get an appointment, but I would also not freak out about a drop of blood from straining. Like Aleron said, if it was something really nasty like Parvo, it's likely that she would have gotten worse by now.
As for fasting, personally I am a fan of giving a dog a night off from food in order to let their system fully purge all the food. Lets you start over in the morning with an "empty" dog.
You also should calm down a bit. I know this puppy is important to you but you need to quit dreading that something is terribly wrong. I'm sure the dog can sense your anxiety and may even feed off of it to a degree. Everything else with this puppy is A-Ok, so it's very likely that this is just a minor blip and you'll both get over it once you figure out what it is.
Some puppies are really bad poopers. I would visit a vet soon if you can get an appointment, but I would also not freak out about a drop of blood from straining. Like Aleron said, if it was something really nasty like Parvo, it's likely that she would have gotten worse by now.
As for fasting, personally I am a fan of giving a dog a night off from food in order to let their system fully purge all the food. Lets you start over in the morning with an "empty" dog.
You also should calm down a bit. I know this puppy is important to you but you need to quit dreading that something is terribly wrong. I'm sure the dog can sense your anxiety and may even feed off of it to a degree. Everything else with this puppy is A-Ok, so it's very likely that this is just a minor blip and you'll both get over it once you figure out what it is.