Hi Ben, many things can cause a small patch of dead tissue like that - teeny tiny caterpillars chewing under the leaf, a patch of light damage, mites, uneven nutrient distribution in the leaf, bacteria from dirty water (e.g. fertiliser mist) sitting on the leaf in the sun. The set of small dots on the lower leaf could suggest a sap sucking insect had a go at it. I would just give the leaves a good wash and keep an eye out for any pests. A
Try not to water over the leaves when you water your tree; you'll be able to rule out leaf burn from water acting like a magnifying lens in the sun. As for chemicals, figs love water more than fertiliser so go diluted when feeding.