My blueberry plants did not flower at all this spring, after being fairly productive for the last 4 years. Our weather was not much different from last year, and I weeded pretty well in early spring. Do blueberry plants typically have a "resting" year?
It is likely a lack of phosphorous. Blueberries are heavy phosphorous feeders and a lack of phosphorous will keep a plant from blooming and fruiting. Add some bone meal to the soil to add phosphorous and this should help.