This is my second attempt making Kombucha. On both attempts, I made a few bottles with mashed blueberries and a few with squeezed grapefruit juice. Both flavorings were heated and mixed with plenty of sugar to make a syrup/puree and left to cool completely before bottling. On the first batch, the blueberry kombucha fizzed up well but yielded a batch that was too sour. The grapefruit kombucha didn’t fizz up at all. I even added more sugar to the bottles and that only helped slightly over the course of the next week or so. I knew that I left the tea for too long and chalked up the lack of fermentation to that. The second time around, I brewed another gallon to add to the maybe 1/2 gallon of leftover tea and waited for a week to get the same result. Blueberry fizzed up fine and grapefruit was left flat. I used two different bottle types and a total of 4 bottles, bottles shouldn’t be a factor. The room temp is about 74/75 degrees and the blueberry batch used to same tea. There was probably more than enough sugar added to the grapefruit juice. Not sure what I’m doing wrong?