Fruit & veg
First time veg gardener
I doubt greatly that isn't potato blight as it's a very fast acting fungal disease and in most cases the entirety of the foliage will be covered and turning into a rotting mess within days. My mint goes like that every year before bursting back into life in spring, it lives in a pot which I put in a very sheltered corner which helps the resurrection come that bit earlier. It's winter though and it just makes most plants look a bit sad 😭
It seems to be spreading quickly and getting worse on the potatoes so I’ll cut off the foliage.
That does look more like potato blight. Your sage looks quite normal for this time of year. Leave it alone and let the leaves die and drop off naturally. It will come back into growth in the Spring when yor mint regrows.
I agree, blight on those potato leaves. The mint and sage look like they have had tiny sap-suckers present, such as thrips.
A trowel in the hand is worth a thousand lost under a bush.