NMG, one bed of my main crop potatoes have pretty well failed; have trouble with that bed, so will add lots of compost and charcoal fines as it seems dry, but rather prone to slugs and snails. Think it was drought this year. The other bed still seems seems to be all right, but haven't tried lifting any yet. My one remaining courgette is only really growing fairly well now, but there are some courgettes forming, so may be ready for harvesting soon.
Pity about your onions Gz. Mine worked quite well this year. I put in autumn sown sets as spring sown don't seem to do as well, and I have never had any luck growing from seed.
lots of manure, compost, weathered seaweed etc added using double spit digging
sorry, the word spud is derived from spade
create good ground and rotate it each crop(follow with a suitable crop for that season)
a couple of years is enough to avoid most disease and infestations
if it is dry, water them, they are closer to swamp plants than desert ones