Unfortunately there's a lot of illnesses that baby puppies are vulnerable to that can kill, even when the symptoms are caught and they're being actively treated in a veterinary hospital. Parvovirus and distemper are big killers, but even more minor illnesses can turn serious fast with puppies, such as stomach bugs, parasites, or canine flu. On top of that there could be dehydration, exposure to the elements if your local weather's been bad in any way (too hot, too cold, very dry, very rainy, etc.), or even poisoning, intentional or otherwise. Puppies are just very, very fragile little guys.
First things first: is there rabies in your country? If so, you should bring this up to your parents, now. If you've been handling these puppies and there's even a tiny chance they had contracted rabies somehow, you need to be talking to a doctor to see if you should get a rabies shot just in case. Don't mess around with it - rabies kills.
As for the survivor, I think the only thing you can do is contact any animal control or rescue organizations in your area, if there are such things. You might also try calling veterinary clinics to see if they can help, or know someone who might help get the puppy to them. You're in a terrible situation, and you've done a lot for these puppies. I'm so sorry it's turned out like this, but it's a wonderful thing that you care so much and gave them a little love in their short lives. Take comfort in that, even if this is tragic and difficult right now.
First things first: is there rabies in your country? If so, you should bring this up to your parents, now. If you've been handling these puppies and there's even a tiny chance they had contracted rabies somehow, you need to be talking to a doctor to see if you should get a rabies shot just in case. Don't mess around with it - rabies kills.
As for the survivor, I think the only thing you can do is contact any animal control or rescue organizations in your area, if there are such things. You might also try calling veterinary clinics to see if they can help, or know someone who might help get the puppy to them. You're in a terrible situation, and you've done a lot for these puppies. I'm so sorry it's turned out like this, but it's a wonderful thing that you care so much and gave them a little love in their short lives. Take comfort in that, even if this is tragic and difficult right now.