worm castings should take care of your boron and zinc, seaweed/kelp for the manganese.
Iron I would be tempted to use chelates though kelp will also provide some iron, as well as copper, manganese, it makes a great quick fix via a foliar feed and some kelp meal in the soil will deliver micronutrients over time as they break down. Basalt dust is rich in iron, magnesium and manganese, though they need to be broken down into plant usable form so they may not provide as fast a fix.
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