Disease markings on leaves

Keltis

The Red Robin and Camelia are next to ach other in a flowerbed, both are established shrubs and about 2 metres high. They each have different leaf discoulration and the Camelia has many leaves virtually black. What are the diseases please and how do I resolve them? Thank you. Terry Kelly, Liverpool 

Pete.8

The 2nd leaf is covered in 'sooty mould'
It's not a disease, but is the result of something that was living on your camelia last year. It's the faeces of an insect - often known as 'honeydew'
Likely culprits include scale insects and some aphids among others.
Can you see any bugs on the leaves or stems? They may have moved on.
It'll wash off eventually, or the leaf will die and be replaced.

All the Red Robins I see have black marks on the leaves - I think it's a 'feature' of the shrub.

Keltis

Thank you. I think my wife will get out her soapy wash on the Camelia after I’ve bathed it with the power hose!  

Pete.8

I hope it not  really big camelia then 😁

Pete.8

I just returned for a walk with my pooch and was looking at the many Red Robins planted in gardens around here.
Most have the same black marks on the leaves as yours, but not all.
I wondered why so I had a google which shows that it is a disease. But not a treatable one.
As Bordeaux mixture is no longer available (unless you make your own) I'm not sure what you could treat it with.
More info here - 
https://www.ashridgetrees.co.uk/blog/photinia-leaf-spo

Keltis

Thanks Pete.8 I’ll  not tell her yet but we have another so I’ll check that tomorrow.