Plant problem

Can anyone help please, we bought an Ornemental Plum tree/bush but it has developed a problem on its leaves, it is on all the leaves & this is the only plant this is on. Pics below

I'd say that was sun damage. Has it been in full sun in the afternoons? When you say "ornamental" plum, ornamentals only usually like the morning sun. Just have to hope that next year the new leaves stay ok if you move it somewhere a bit more shady. Is it in a pot, can you move it? I did the same with one of my acers the same colour as that, it didn't like the full sun on the patio, so my leaves went like that and then all dropped off, instead of giving me a bit of autumn glory by turning red! That's my take on it anyway.

Yes ornamentals can easily get sun damage but I'd say those little tracks are an insect of some sort.

Thank you for the replies