I don't know why your plant is unhappy right now, I would just give it time. I have this species of Ficus (along with several others), they are quite robust plants and can recuperate from some loss of foliage. I think your lighting is quite good, and there is no reason it should not be putting out new leaves now..., even now in mid January, mine are, and I am several hundred miles further north of you. I would withhold feeding until it pulls out of its current funk. Also, try to season it outside, it makes a huge difference with Ficus (May through September). Good luck!
