I suspect you must blame the winter weather. In my climate we had a late frost in April just as the hydrangeas were setting buds and therefore my hydrangeas also had very few blooms. The branches that did flower were the inside ones tucked into the middle of the shrub protected from the cold. Give the hydrangeas another chance this coming summer and do not prune them now. Pruning in the fall always stimulates new growth which is more tender to the cold. You can also try moving your hydrangeas to a more protected spot close to the house or cover the plants with a sheet on nights in late spring when a frost is predicted. Keep growing, Marianne Binetti