A couple things to check.
First, check soil moisture by sticking your finger in it all the way. Like most plants Ficus don't like having "soggy feet" (and are very prone to root rot) but when potted they need regular, deep waterings. So far all Ficus problems I have seen were caused by water: overwatering, underwatering (or no water at all), one inch of standing water in the undervase...
If you have an undervase I strongly suggest filling it with gravel to avoid standing water and excessive moisture issues.
Second, tropical Ficus don't like temperature swings. That's why they should always be kept away from AC units, heaters etc. They also don't like sunlight extremes: I've found the best place for them in the cold season is about 7" away from a South facing window, while during the Summer they do well under a curtain.
But, again, I strongly suspect yours is a watering issue.
Finally, fertilizer... these are not plants that need as much liquid fertilizers as some websites say. They seem to be doing well with 2/3 doses a year, which can be avoided entirely if the plant has been freshly repotted. As I always say to people using too much fertilizer you should be growing cauliflowers and eggplants.
