According to the posted pictures, the cause might be root rot diseases. in this case we should exam the root of the plant in order to be sure.
Regards
Raed

Whoa, Raed. Let's not start digging plants up before we gather more information.

Sandy, I believe that this is one of the Prunus laurocerasus cultivars, perhaps the very popular Otto Luyken but I would like you to verify that. Do you think that these are established shrubs or recently installed by the previous owner for 'curb appeal'?

Do you have an irrigation system? Have you had a considerable amount of rainfall this season?
Finally, we need to know if the soil in this location drains very well. Is the soil clayey?

All of this information would be helpful in trying to figure out the problem. It's very much like the pieces of a puzzle.

Whoa, Raed. Let's not start digging plants up before we gather more information.

Sandy, I believe that this is one of the Prunus laurocerasus cultivars, perhaps the very popular Otto Luyken but I would like you to verify that. Do you think that these are established shrubs or recently installed by the previous owner for 'curb appeal'?

Do you have an irrigation system? Have you had a considerable amount of rainfall this season?
Finally, we need to know if the soil in this location drains very well. Is the soil clayey?

All of this information would be helpful in trying to figure out the problem. It's very much like the pieces of a puzzle.

I think it does warrant looking underground. There is no need to dig a plant up to get down there and examine what's going on with the roots and the soil.

I would also be interested to know how close the three shrubs are to each other and how close to a house they're planted. A photo of all three would be helpful.

If that sickly one didn't have dead stems mixed in with healthy ones, I might suspect herbicide damage. In fact, I might suspect it anyway. For example, if the healthy one is around a corner from the two that are suffering, it might have escaped drifting chemical. Does that make any sense?

It certainly won't hurt to pull up that dry one (middle photo) and take a look at the root system.......it is not going to come back to life any time soon :-)

I seriously doubt it is anything to do with herbicide or chemical damage - the symptoms are just not indicative of that. But it does look suspiciously like a water issue. I'd follow Dorie's path and ask those same questions - amount and frequency of rain versus irrigation, when planted, soil condition. Often times too much water and not enough water will produce very similar appearances. And water - or lack of it - is the number one cause of plant failure.

Just from the photos, I'd make a very quick guess of newly planted and lack of water - the plants are small and the soil looks bone-dry.