Your plant looks like Ilex crenata and it is probably having problems with the rooting environment. If the shrub started looking shabby last year then drying out of the soil at that time may have been the start of the syndrome. Otherwise I would suspect root rot due to water molds. Especially if just the one is like this.

Yeah, I suspect that it was water related. When did it go into the ground? Japanese Holly are very/extremely tolerant of heat, humidity, ice, snow, cold, etc. once established. But if watering was not regular upon transplanting, might have never really gotten properly established. I would cut out any dead wood. It might recover this season though..., they growth rate in moderate in my neck of the woods and usually can't keep up with the pruning of these guys.

These were planted when I bought my house three years ago. They have been healthy until now. We had a very bad drought though last year. I will try running a soaker hose through that flower bed.

perk your soil ...

https://www.google.com/search?q=perking+soil&ie=utf-8&oe=utf-8

figure out how water moves thru it ..

dig small holes with a hand shovel .. and stick finger in soil.. to figure out how and when to water ...

and then water accordingly ...

just throwing down a soaker hose.. and hoping for the best.. may or may not solve your problem ...

and note.. a 3 year established plant.. should not have problems in some drought ... as pointed out above ...

ken

Japanese hollies can be finicky about watering. Not too much; not too little.

sounds like too much was the case this time