3 plants dying
The shrub looks like a pyracantha. We notice some thorns along the branches.
We are not sure what you may be dealing with. This shrub is susceptible to several fungal diseases (scab, cankers, fireblight) as well as poor site conditions like poor drainage, soil compaction, etc.
This shrub is very hardy and we recommend pruning out the dead plant material during dry weather. Monitor the plant and wait for new growth. If you notice more symptoms, send them to us so we can see what you are dealing with.
In general, if you are dealing with diseases, the best option is to select disease resistant varieties.