laurel are often attacked by vine weevil. The vine weevil grubs eat the roots over the winter, often causing the symptons you descibe. The grubs hatch out during the spring this allows the roots to recover enough to keep the plant alive but stop it growing away strongly. The only visible sign during the summer are distinctive notching of the leaves. You would think they would attack all the plants at once but we often find one plant in a row can be attacked. If you dig round the base of the worst plant you might still find some of the grubs - white about half to one inch.
we find biological control (nematodes) works extremely well