This kimchi was prepared yesterday, and today it is sour enough to be packed into smaller containers and stored in the fridge. The reason why it turned sour so fast was probably due to the addition of the kimchi fluid from the last batch into the one I prepared yesterday. The fermentation is very active, with lots of bubbles. It needed to be arrested or slowed down by keeping it in the refrigerator.
From my past experience, the fluid of the kimchi will turn thicker after one week in the fridge, and it will taste less salty. Thus, it is okay to prepare a lot in one batch as it gets better with age.