Welcome Teena. From another Tina.
Hydrangeas are heavy feeders and need food as early in your season as you can get it to them. Acidic food is best like you would feed azaleas or camellias. And then regular feeding through your
growing season. Do you prune them at all? Different types have different pruning needs and seasons.
In California where I live, I feed them all year long even when dormant. I don't have your winters to contend with. Maybe someone else with more appropriate climate knowledge will come along and help you out.