Are you pruning your hydrangeas? Many hydrangeas flower only on two year old wood so not pruning gives best chance of blooms. Cold spring weather can also nip those flowers in the bud stage and too much shade adds to a lack of flowers. The large leaves leads me to believe the plants are healthy so too much shade or cold spring weather could be to blame. Consider a more cold tolerant hydrangea such as the mountain hydrangeas or the varieties 'Let's Dance" and 'Tuff Stuff'. Keep growing, Marianne Binetti