Vinegar-tasting kombucha

[JulesRUs]

Hi, I started brewing kombucha about two years ago, and used to have 5 batches going at once. Then, I was traveling a lot, so I condensed to one and kept it in the refrigerator to help it not ferment. It was there for 6 months or so. Now, for the past 4 months, I haven't been able to get a good batch--it seems to turn straight to vinegar, even when it still tastes very sugary just two days after making a new batch. I've tried using more sugar, putting it in different places with different heat, testing it every day... In all these situations, it's still going straight to vinegar. Does anyone have suggestions for this?

Julia