Corydoras are micro-predators, feeding on small creatures in the sand. No fruits or veggies are good for them.
Platys will pick invertebrates out of algae, and eat some algae, but again, they aren't straight up herbivores. Here they have eaten frozen, then thawed zuccini slices, but I wouldn't make it a core diet. They picked at food I was putting in for Ancistrus species.
Bananas and strawberries are great for the few 'fructivores' in the hobby (most fruit eaters are larger fish than we keep in tanks), but both can foul the water fast. They're high sugar. If you have herbivorous fish and can get insecticide free romaine lettuce, frozen and thawed (that works like blanching) it's a good option.