@Tam and @Walt are correct... Increasing the volume of creamy flavors (Vanilla, Malted Milk, Cream, Ice Cream, etc.) will reduce the "bite" of the fruit flavors. Like Walt, I've found that certain brands of fruit flavors are much harsher than others, and some of the "candy" flavors are very citrus-acidic and artificial tasting (just like Tam said). I also prefer Capella and TFA (The Flavor Apprentice) fruit flavors over others.... CAP are some of the best IMO...
I would also suggest lowering the candy flavor (or eliminating it all together) and play with the ratio of Blueberry and malted-milk/ice-cream flavorings until you find the right balance. Mix in 5ml - 10ml batches until you find the ratio you like best... then you can make gallons if it if you wish