These plants are a type of ground-covering Juniper; there are several types commonly used, and this one appears to be either Japanese Garden Juniper (Juniperus procumbens) or Shore Juniper (Juniperus conferta). All ground-covering Junipers grow best in full sun (6 or more hours per day in summer) and soil that is very well-drained. They have limited tolerance for compacted, heavy-clay soils or those which are often wet.

When under stress, or in wet conditions (such as being under a sprinkler system or in a rainy, cool spring), they can contract any of several fungal infections that cause needle browning and some branch dieback. Unfortunately, root dieback from similarly-wet conditions can also result in branch dieback, so the two causes are difficult to tell apart. Neither will improve with intervention, though, since fungicides have limited benefit in each situation as the damage has already been done by the time the symptoms appear.
https://extension.umd.edu/resource/juniper-twig-blights

If ice-melting salts are used on the pavement, these can accumulate in the soil over time and damage sensitive roots. Junipers in general aren't the most salt-sensitive plants - their tolerance is fairly high, though this depends on species - but even they can be overwhelmed in some circumstances. Additionally, if the lawn on their other side is fertilized heavily or treated with certain weed-killer products, they may be negatively impacted.

All you can do for now is to trim out any dead growth, keep an eye on any yellowing or off-color branches (as these too usually don't recover), and make sure the planting isn't being over-watered. If a downspout empties nearby, for example, re-direct it further away if possible. You do not need to fertilize or spray anything as they will not help the plant improve. If the plants decline too much, or if the pruning of dieback leaves too little growth or an unappealing shape, the most practical option is to replace them with new Junipers or an alternative plant.

Miri