Blackcurrant leaves turning yellow

[Dagz]

Hello folks. I have already looked for an answer on other places but none of them seemed to describe the exact problem my currant is probably having.
Some say it is rust. But when I check the photos on the web, it does not look exactly like that.
I don't remember what variety of black currant I have. I think I got it in one of the discount supermarkets, either Wilko or Pound Stretcher.
Here are some photos from the top and bottom of the leaves.
The bush has plentiful fruits and shoots new leaves.
I have not noticed any insects around it, not even aphids.
What could cause this yellowing from the middle of the leaves and is it harmful to the plant? Can I do something about it?
Thanks.

[JONA]

Hi Dagz,
I know that this is unusual on currents...,but that looks suspiciously like red spider damage.
To see them you need a ten times lens s they are so tiny...but as they develops they do form a sort of webbing .
They are not actually a spider, but a mite.....only Six legs!
Providing the damage does not spread .. don't worry.
There are predictors you can get on the web ...phytoseiulos eats them. Or there Are sprays available. Just see if it gets worse.

[Dagz]

Hi Jona, thanks for the reply.
By predictors you meant predators, right?
I will keep an eye on it.
I have removed a few affected leaves. Could that help?
I also have a neem oil I use with dish washing liquid solution on aphids. Can that help?
Thanks.

[JONA]

Hi Dagz.
Sorry about the spelling error...your correct, I did mean predators.
Removing the affected leaves if that is practical will help, spider mite lay large numbers of eggs which they protect with a webbing that protects them from sprays, so anything that removes these initial infestations will help to stop further spread.
Neem Oil, as I understand it, does have some effect on spider mite but in serious attacks it is best to follow up with predators as well.
I think the basic problem is that there are few approved chemicals that will take out both adult and eggs of the mite.