Well, my gut tells me the maggots might have been the problem. Young birds need time to develop before eating such things. I might be totally wrong with that answer but it is what stood out to me when I read your reply. You may now want to up the protein to at least 28% suggested, just leave out the maggots for the time being. The vitamins in the water may have been what brought them out of their shakiness also.
The reason I asked if they were from the same parents was I was thinking that they maybe passing on a disease to the chicks that their weak and undeveloped immune systems were not able to handle right away. If you have a vet around you that you could show that short video to you might get a more definitive answer.