My kombucha is suddenly very sour. What could be the reason for this?Updated a year ago

Is it by any chance summer and very hot outside?

The bacteria and yeasts work faster in warm temperatures. For your next batch, use a little less of the very acidic batch liquid and let it stand a little longer. Try it every day and then fill it when you like it. Note that in the course of time, even in the refrigerator and especially during the second fermentation, it still sours a little.