Hi, I had something similar happen with my common garters, she gave birth to one on the 6th July, i saw it and searched for more but couldn't find any, then she gave birth again on 9th july to 3 live and 9 dead. Unfortunately i think i may have disturbed her when i saw the one and assumed she had finished giving birth.

The four live are a good size about 4inches, they are all doing well.