@res I agree with @Woodgreen if you look into the hedge you will see some of the yellow leaves, by cutting back you have exposed these to the light? I know you have had concerns before. It's Laurel it will recover that's for sure.
I have worked as a Gardener for 24 years. My latest garden is a new build garden on heavy clay.
From a sprayed point of view, that would need to be sprayed by a very large nozzle at very low pressure, and I can not think of a product that would cause that.
Marks on the leaves of different types of plants, so either an unfussy insect that isn't specific to a particular type of plants, or maybe if you had a hailstorm that could have caused damage when the leaves were newly-opened and more delicate?
Doncaster, South Yorkshire. Soil type: sandy, well-drained
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Gardening in Central Norfolk on improved gritty moraine over chalk ... free-draining.
have you looked on the underside of a leaf.