Yes although healthy to eat the blueberries are pretty acidic so if you suffer from acid reflux or other stomach issues then you should avoid eating too many blueberries because of the blueberries being acidic.
Besides blueberries being acidic other foods are also acidic such as honey, blackberries, strawberries, raspberries, caffeine, chocolate, alcohol, mint, tomato, onion, and garlic.
Those are all pretty acidic foods that you should avoid eating too much of if you have acid reflux disease or suffer from any other acidic stomach issues.
But you can usually eat those foods in moderation but if you have stomach issues that get worse when eating those or blueberries then it's best to avoid those foods or at least slow down on the amount of those acidic foods you eat.