My ficus bush has turned yellow on the leaves, and they are dropping off at a farely good rate,several leaves a day. I live in Idaho, were the tempetures are cold. I do not know if now that we have started our fireplace could be the reason for this? It is getting really good light, and is not by any cold drafts, and it is not in direct contact in any way from the fireplace. I also have a humidifier running in the same room.I have always had good luck with this plant, really never any problems until now. I have had this plant for 4 years now. I would love to have any advice you could give me.
Thanks,
Kellie

You can get rid of the humidifier if it's just on for your ficus. Ficus can do very well without one as well as most indoor plants. Cold and wet could be the problem for your leaf drop. Let the soil dry halfway down in winter months, some people let it dry out, let the top inch or two dry out in the summer months before re-watering.
If you have moved it to another location within the house or recently re-potted, both can cause leaf drop, as well as over-watering or under-watering. Also, it never hurts to check for pest.
Hopefully the roots are ok and with the right care, new leaves will come back, but you'll need to be patient. You might have to do some pruning after your ficus stabilizes.
No fertilizer in winter.