I'm so sorry. 
It's entirely possible that something else was going on inside. When they are so small it's very hard to know. There could have been issues with development due to genetics or hatch. I think you did everything that could be done. Sadly, not all of them make it. Some of them just fail to thrive.
For future, the nutri drench can cause diarrhea if used for too long, but it's a very good short term supplement and can help save a bird. Vitamin B supplements really have no negative side effects.
It's entirely possible that something else was going on inside. When they are so small it's very hard to know. There could have been issues with development due to genetics or hatch. I think you did everything that could be done. Sadly, not all of them make it. Some of them just fail to thrive.
For future, the nutri drench can cause diarrhea if used for too long, but it's a very good short term supplement and can help save a bird. Vitamin B supplements really have no negative side effects.
