Spite mites might have caused some foliage stippling damage (it's hard to see in the one photo, but there might be some light to moderate stippling on the green leaves), but they would not cause all-brown foliage or branch dieback. Even if they were present, they are not the main cause(s) of damage and do not need to be treated compared to whatever other intervention is needed for the other factors causing damage.

To be fair, cherrylaurels are often used as foundation hedge plants, but yes, it's not a great environment for them, and those types of site conditions can stress just about any plant used there. Issues can arise from changes in soil acidity over time from a concrete foundation, compacted soil and more limited root room (given the proximity of the foundation), and extremes of moisture from either poor drainage (or inundation from a nearby roof downspout outlet or overflowing gutter, if applicable) or a "rain shadow" from the house itself or any roof overhang. Regular pruning, even if well-tolerated by the plant in otherwise-ideal conditions, can add to plant stress and often plants used as hedges or foundation plantings are pruned too often or too heavily, which can predispose them to certain pest and disease issues.

Stressed or damaged plants should not be fertilized unless a soil nutrient deficiency is the primary issue, which is not the case here. Adding nutrients (especially if the soil already has plenty) can worsen root stress and compromise the plant's ability to recover. A laboratory soil test is the only way to confirm if a nutrient deficiency exists that will impact the roots.

The white markings on the bark are a normal feature of the bark of many plants, and they're called lenticels; they're essentially akin to the "breathing" pores present on foliage, but much more visible. Some plant species have more prominently-visible lenticels than others. It does not look like a key pest of cherry laurel called White Prunicola Scale, which would be more bright white and clustered into denser aggregations on the bark, especially near the thicker branch bases and on the undersides of those branches. This is not to say the scale insects aren't on any of the affected plants or plant parts, but that we don't see them in the provided photo.

The dead branches with brown foliage could have several causes, including drought-induced dieback (either by itself or due to an opportunistic fungus like Botryosphaeria canker infecting them), peachtree borer activity, damage to the lower bark (near or just below the soil line) from vole gnawing, physical breakage (could any heavy snow or ice have weighed-down or snapped the branches?), or root loss due to extremes of soil moisture. In either case, the original issue may not matter too much since the only recourse is to prune off the branches will all-brown foliage because they will not recover.

With more photos of the symptoms and how the shrubs look overall, we can provide more feedback and narrow-down what the likely issues are/were, but if you want to replace the plants, be aware that anything in such a location can be vulnerable to stress, either from soil drying (requiring more attention to watering during drought) or soil saturation, and reflected/radiated heat from the nearby house wall. Whether you replant cherry laurel or use another species, choose something that stays as close to the height you need the plant to stay (if blocking windows is a concern) without having to trim it to get the plant to fit the space. Knowing more about the site conditions (typical soil moisture level and drainage, how much direct summer sun it receives, if deer browsing will be an issue, what mature height/width the area can accommodate, etc.) can help you determine which other plant species should do well there. We can offer some suggestions to get you started if you want, once we have that information.

Be aware that some products in the Bayer product line (like the one you listed, potentially) contain an insecticide ingredient in the chemical class called neonicotinoids. Two examples of active ingredients in that category are imidacloprid and dinotefuran, both of which can be commonly included in systemic pesticides that manufacturers offer "over-the-counter." You can find the active ingredient list on the product's label (usually on the front label, but also on the more extensive label on the back of the bottle). In Maryland, neonicotinoid insecticides are regulated can only be used by a certified pesticide applicator. You can learn more on our Pollinators and Pesticides web page. If their use is warranted (often it's not and other measures can solve the problem), you would need to hire a licensed applicator to buy and apply such chemicals for you. Bayer and other manufacturers have reformulated some of their insecticide ingredients in products that combine several pesticides into one bottle, so check the label -- some that used to contain a neonicotinoid might be using another ingredient instead, and we can't tell from the product name alone which ingredient mix is in that specific product without looking at the label. Additionally, while some combo products include a fungicide alongside the insect and/or mite controls, the fungicide cannot cure any existing disease (it only helps protect healthy growth from infection, although it's not foolproof), and often diseases causing branch dieback are not well-controlled by such ingredients.

Miri