Hi & welcome! Sounds like you might have had fungus gnats as well as centipedes in the soil. Both inhabit soil, but don't bother plants unless/until the dead organic matter in a pot has been consumed. At that point, they could start eating roots. The process of eating the organic matter (and returning it in the form of poo) radically changes the soil structure, turning larger particles into "dirt." Once that process gets to a certain point, the roots can begin to suffocate & rot from lack of oxygen/increased water retention. I would repot your tree while the weather is still nice. If interested, you can find many discussions about FL fig in houseplant forum. Raid could be toxic to plants as well as critters...

If you're watering when the soil "feels damp when I put my finger about an inch into the soil, it's almost a sure bet you're over-watering. Use a wooden dowel (from a hardware or big box store), ends sharpened in a pencil sharpener, stuck all the way to the bottom of the pot to tell you when it needs water. If the dowel comes out wet or stained dark with moist soil, withhold water until the point in time when it first comes out clean/dry. Also, flush the soil thoroughly the next time it needs water. Your watering method ensures all salts from your tapwater and fertilizer continue to accumulate in the soil. The high level of salts + the plant's inability to move water efficiently because of waterlogged soil conditions are pushing the plant to a death by thirst in a sea of plenty. Al

I found a topic while digging through posts from Gardenweb past-is this the exact issue you're having? http://forums2.gardenweb.com/discussions/3396928/new-growth-help?n=16

Just keep eye on the healthy leaves. If other leaves stay healthy in 2 or 3 days, then nothing to worry. If the symptoms spread further, maybe soil nutrients deficiency is the cause. No need to cut off any leaves since they still able to do photosynthesis, but if you think remove unhealthy leaves will make you feel better, then go ahead. Seems that you have enough healthy leaves to support plant growth.