Get a soil testing kit and see if the soil Ph is too high. If it is, iron or manganese deficiency could be the cause. If not then you will have to consider insect, bacterial or fungal causes. Once the cause is found, then the cure will follow.

Well, they all seem to be suffering the same thing - diagnosis from me as far as the rose is concerned is a shortage of manganese and /or iron - whether that's also affecting the other two plants, not sure, but could be.

Maybe, but why now? They have never done it before. And other shrubs near to them are ok, but there are others a long way away which are also affected.
Weather?

It is weird - have you put anything on the soil in the last year or two - composted materials or the like? Changed feeds (though that seems a bit bonkers too, you'd have to only used something new in the affected areas).The weather wouldn't explain why you've got areas in the garden that may, or may not be, short of particular nutrients suddenly. This might be a question for the RHS...

Don't suppose its the cold wet spring?.....
something about washing nutrients out of the soil.....or cold affecting young leaves, my fuschias seem a bit like it...

Going to try spraying with Epsom salts, see if that helps. Magnesium deficiency would give this sort of leaf problem. We shall see!
Thanks folks.

Are they all in the same area of the garden?
Waterlogging is one possibility that could affect the take up of nutrients. Or could they accidentally have been caught by weedkiller (fine spray drifting)?
If you have camellia/rhododendron fertiliser available you could give it a go (rather than getting in Epsom salts) it will have the nutrients which are the most likely suspects. I'd also check whether the roots are getting congested - another reason why they can't take up nutrients.

I though magnesium Ob.....but whats happened in that area to cause it?......

Nowhere near any place where Weedkiller has been used. The shrubs are spread out through the garden and even some in the hedgerow.
There are shrubs of the same family next to the affected ones which still have green leaves.
Our garden is extremely well drained so no problem with water logging.