Laurel defoliation help

[Conor Wright]

This one has me scratching my head...

I planted this laurel hedge for a client just over two years ago. I replaced a handful of failures last winter and noticed some other plants were not looking too good. I was passing today and saw that more had declined with some completely dead.

most of it has done reasonably well however there are about 30-40 plants showing these symptoms. 

This hedge got the same treatment as all the others I've planted over the years and I've never encountered this many losses.

Anyone have any ideas? 

 Btw its Unlikely to be drought. Its a wet site, they wanted beech but I convinced them to go with laurel at the back as I thought it too wet and peaty for beech.

Same batch of plants from the same nursery were used on other sites with little to no losses. 

The client did add sheep manure to the soil about a year before it was planted but I don't see this being an issue.

About 20 of them are together with the remainder dotted around the site. About half the hedge is thriving.

The ones I replaced are not doing well either.

Anyone recognise a disease from the pics? 

I'm probably going to dig it out and replant either way but I'd like to know the cause.

[Lowestoft Firewood]

Have had similar on a batch we planted. Most have done fine but ones like this croaked

[Excels1or]

Phytophthora?