Heirloom vegetables grow more slowly and spoil much more quickly than modern crops. This is because modern crops have less nutritional value - https://jeroenvanbaar.substack.com/p/data-dispatch-4-the-falling-nutritional
That article recommends eating a better diet. Sure. Seems a bit idealist. Here's some more actionable advice: everyone should take a multivitamin and magnesium glycinate. If you live somewhere that gets a winter take vitamin D too.
I'm speaking from experience here, I used to get sick every winter and my skin would get so dry it would crack and bleed. Take your vitamins.
Careful, many "vegan collagen supplements" are not actually collagen, they're other things which supposedly increase collagen production. (I don't know if there's any evidence that works.) Collagen is a mix of proteins, which you could get microbes to produce. (And then we could make vegan gelatin from it.)