Don't fuss about the fertilizer one way or the other for now, don't overdo it. Was there some reason you let it get so cold (considering how readily you can see weather now online)? Anyhow, back off on watering - only do it when more of the soil is dry than you normally would, but do it well when you do it. If leaves are meant to come back, they will within a few weeks or so, but no one has a crystal ball after all. Green on the trunk is good of course.

Thanks for your reply,

I don't think I was clear in my first post, when it got so cold outside, I brought the tree inside, so he was never exposed to such cold temperatures:)

Oh.. just re-read and you're right about bringing it in. Well, all I can think of is that the change (any change) from such great light (compared to indoors) outside, plus maybe more (or less?) water than it was getting, etc. etc. caused it. So many trees lose leaves when changes take place but if they get good care, usually come back.

I've also noticed one key thing.
I can see some small leaves trying to come in, however after a day or so, the little buds just turn black and die :-/

Is this a sign of something ?

It's a sign they're not growing, but why not is the question... Not being there, I can't say if it's overwatering (i.e. too often), or not enough sun, cold temps, or not enough humidity. You're there, so would need to guess. Have you looked closely at the triangles between trunk and leaf stems for tiny webs and/or spider mites?

what is your watering protocol ...

a tree doesnt not need as much water.. indoors.. as it does outdoors ..

so .. if you are watering.. like you did outside.. during the heat of summer... then you might be watering too much ...

and one sure sign of rotting off the roots... is dying off of buds ...

i highly doubt you need the humidifier ... even up here in MI.. where it was single digits for a week... the furnace has not burned the humidity out of the house .... but i am no bonsai savant ... lol ...

i think you are on the verge of loving it to death... when i get myself to that point.. i ignore it for a month.. and half the time.. it recovers.. mostly because i have quit messin with whatever ...

it is severely stressed... it is not hungry ... i would stop feeding it ...

ken

Thanks for the replies guys.

I checked the tree for any mites or webs, and found nothing.

Ken, I water the tree whenever I see the soil is dried up. I understand I'm not supposed to water it as much now that it dropped all the leaves.

I agree that maybe I overthink it a bit now, and I should just leave it be for while.

I took some closer shots of the tree just to get them out there for you guys to see what's happening.

Scratch the trunk halfway up and see if it's still green underneath... still living. The branches in your picture are dark... could be watered too often.

Hi Luke , Ficus grows naturally where it's hot and wet. You are not watering it enough. You should not dry it out before watering again. Humidifiers are a good idea, otherwise it will not come back into it's growth phase again. Growth period for figs is the monsoon, when it really pours.....Your pot should have good drainage.