Plants need micro nutrients to survive along with the light and water. Among those nutrients are calcium and magnesium. When I give my plants nutrients with extra magnesium, the leaves turn darker green. Once I gave them too much mag. And the leaves looked similar to that. I don't want to say that's the deff. Culprit for your problems, as there too many variablesin the situation. But you might want to repot the plant in better soil, more suited for cannabis, not a fig tree.