I've got 4-5 hydrangeas that are 2 years old. They were full of blooms but as you can see are drooping and yellowing some. I'm in North Carolina so the heat and humidity could be the problem. They've gotten good water and extra when signs of wilting show. I've never fertilized them except for overspreading from the lawn. Can anyone suggest a solution? What and when is the best time to fertilize...early spring and fall?