We have two hydrangeas, 3 years old. This year one of them appears to wilt rather quickly requiring me to water it by hand. Because of their location I water them every day for 10 minutes using a drip system which I installed 3 years ago. The second hydrangea is fine. They both are watered by the same system. I added an additional head to the system at the problem plant but appears to have no effect. The leaves wilt and the flowers drop over. After I water them by hand they revive. Any thoughts would be appreciated.