Were weak spartan babies killed

Yes, and they were either thrown off a cliff or drowned. They figured the weak were no use to Sparta because its main focus was its military.

Yes, if the babies were weak or sick, they would be dropped off a cliff or turned into a helot, a slave to the Spartans. Spartans only looked for strong babies for their military. If the baby was weak or deformed, it would be no use because they proved a weak spot in the phalanx. They needed someone to watch their allies backs while maintaining form.