Doing a one gallon batch myself. Had a taste yesterday, so far - yummy. It's in the primary still but yesterday was the first day I couldn't detect any sweetness. It has a long way to go yet.
I was very surprised. They weren't exactly the berries I wanted. Purchased from a local small organic blueberry farm (Legacy blueberries). Some had some good taste but over all, they were more sour than flavorful. I was not happy (til later)
After a freeze and thaw, adding campden and letting them sit, I added sugar and water and then tested for acid. Couldn't read a PH test strip as they are dark red. Ran a TA test and it was only .30 TA.
It's been a bad spring here and after tasting the blueberries, I didn't think they would do well. They surprised me and made a great juice and fermented to a good wine taste. I did end up adding more acid blend, and 1/8 tsp tannin. Using Montrachet yeast.
I also added 1 tsp yeast nutrient and a little more than 1/8 tsp yeast energizer as I heard that blueberries are harder to get started. I had no problems.
When I added sugar, I added 1/2 less than the recipe - which is what I had previously done with a raspberry and blackberry. With the blueberries and 2.5 lbs sugar, the SG was 1.102 ...I was wanting 1.090.
So, as a suggestion, before you completely follow a recipe, test for PH, TA, and sugars ...it seems that blueberries vary greatly.