I basically use the recipe in NT, a 1-gallon glass jar & 4 tea bags (organic Darjeeling) & 1 cup sugar. Brew time has been about 1 week now that it's so warm where I am. At that point there's not much sweetness left (tho there is still some) & there's lots of fizz. I've been using the same scoby for about April.
I do have a couple scobys in a scoby hotel in the pantry. Maybe I'll just start with a new one next time. But I'm just curious as to why this aftertaste has developed. So far (after drinking a glass from each of the last two batches) I'm still standing so it hasn't made me ill.