Why did all of my kits die?

My one year old Satin gave birth on Tuesday to six squirmy little bunnies. It came to a surprise since apparently she was already a week into her gestation when my gf and I rescued her. A crazy neighbor said he'd kill it if she didn't make her way off his property soon. So when I come home, I cut up a cardboard box, put a towel down, get the nest my Satin made and put the kindling in it. Cinder (the name of the mother), ended up not taking care of it for whatever reason. We think she may not have been producing milk. On Day 3, we had our first mortality. I didn't see her around, but research showed me that she spends a few minutes to feed and she isn't around them the rest of the day. I took the remaining to a vet, and got a syringe and bought KMR. I fed them RIGHT as I got home (about noon) about a CC of the KMR. I had to work, but I figured they'd be okay until I get off work. I arrived home to find two more dead. I left them a lukewarm water bottle since they were cold. They had plumped out a bit which was another good sign. Yesterday, our last one went into eternal sleep. I can't figure out what happened since I was acting as mama and tried to give them everything they needed. Were their bodies too weak to feed? The vet said two feedings of one CC, and I figured if the feedings were hours apart, they'd starve. For a guy, I still feel horrible about all f them dying. I shouldn't have waited as long, but even so I did what I could for the rest and it didn't help. :(