Looks over watered to me, but I could be wrong. First take a powerful magnifier loop and look closely at the leaves and rule out any insects. Second, go to the base of the hedge and dig down beside the plant hand deep or deeper and feel the soil. If it feels too dry then water it more. If it is too wet stop watering it and arerate the soil.
It is very helpful for plants, especially sick plants, to aerate the soil around the base of the plant between waterings and keep the soil loose. Take a hand cultivator and gently work the soil around the plant will allow the roots to get the oxygen they need for transpiration.