Why the spring on (-) polarity at the alkaline battery 1.5v gets eroded
The quality of batteries. Branded batteries can be of bad quality. Be cautious of Panosanic or Sanio batteries;
Damaged batteries, e.g. the parcel full of batteries have fallen to the floor during transportation, and interior and exterior battery structures get damaged, causing the leak shortly;
The position of storage. Note that third battery did not leak, because it is located upside down.


The pic of the batteries would help to diagnose the problem better.