The dieback of a section of your plant is a symptom of peach tree borer damage. This is a common pest of laurels. This insect bores into the wood, usually right at the mulch line. Check around the base of the plant for signs of physical damage -- chewing, cracking, tunneling, frass (sawdust-like material). The chewing of these insects results in girdling of the trunk and the plant cannot take up water and nutrients -- resulting in dieback. Here is additional information about borers. https://extension.umd.edu/hgic/shade-tree-borers If treatment is desired, a landscape professional can provide a systemic pesticide.
The holes in the leaves are another issue. This is called cherry shot hole disease and it is quite common in laurels. https://extension.umd.edu/hgic/plants/cherry-shot-hole-flowering-cherries