Negligence, definitely! Murder...I don't think so. Not unless I'm missing some information.
The baby died.
It showed definite signs it was dying, and they ignored them, failing to take the baby to medical professionals.
Negligence resulting in death....definitely more than simple negligence.
Failing to clean my dog's cage is negligence.
Watching a baby starve to death, and doing nothing about it should IMO, be classified slightly different.