My fig tree leaves look light green then darken as they age, the veins start out yellowish and end up nearly white.
Check the underside of the leaves you are worried about (sometimes figs can be troubled by leaf miners, and other leaf tissue eaters, DE sprinkled on the underside will help a lot with that).
You can always sprinkle some Epsom salts around the drip line of the trees, they do seem to use a lot of minerals for fig production.
I use about a cup of Sea-90 around mine every couple of years to help with additional minerals. (My fig trees are only three years old and about 15 feet in diameter now)
Compost teas really help figs develop strong resistance to pests and diseases, mycorrhizae are good to add too.