Hello everyone,

I would like to apologize in advance if this is not the right section of the forum to post this or if I should have approached the issue differently - but all of the related posts that I found haven't helped me much.

So here goes my story:
Towards the beginning of the year I've purchased a small Fukien Tea from a local flower retailer. In the beginning it looked nice, vigurously green and flowering. Several months in I've noticed it had some small flea-like insects around the soil that used to come out whenever the temperature was warmer; I then used some "bonsai" pesticide and after a few weeks it seemed I got rid of the problem and the tree was a-okay.
Fast forward to ~October I decided to repot my 3 trees (Fukien, Chinese Pepper and Hoop Pine) since I've noticed that the soil they were in (some dense peat as far as I could tell, the cheap one all the "bonsai mass producers") became very compact and watering them wasn't efficient at all.
So I did, and used a mixture of 4 parts volcanic rock, pumice, zeolite + 1 part akadama. Later on I've also added a layer of finely chopped sphagnum moss to maintain a the soil a bit more humid.
All was pretty much well and about a month ago I've also sprayed all of the trees with a mild combination of insecticide and acaricide (aktara+nisorun if it rings any bell) since I've noticed some white spots on the FT that seemed mushy to touch (didn't feel like mold so I thought those might be some spiders or mites); got rid of that issue as well.
Throughout the whole period after repotting my FT and Pepper were placed in a humidity tray on a southern facing window sill, somewhat close to a heating source, regular temperature around 20-23 degrees Celsius,with a fluorescent 6500k bulb ~20cm away from them providing additional light in a 8h on/4h off schedule since the days are quite short and cloudly back here (Romania).
I tried to water them each time the moss on the surface and the soil around the trunk seemed dry, which meant the pepper got daily watering and the FT pretty much the same or at 1.5 days intervals + misting of the leaves.
Last week-end I was out of town so before I left on Friday morning I watered the trees. When I came back on Sunday afternoon the pepper was a tad wilted but came back shortly after watering (it did that before); however my FT was extremely dry, with the leaves loosing their intense green towards a lighter one, being wilted and turning drier. I've immediately watered it but it didn't bounce back - I'm suspecting the issue was that across the week-end the outside temperature increased unsuspectedly from -2, 3 degrees C to about 10-12 and the inside temperature wasn't adjusted accordingly + lack of water for 2 days +. I've turned down the heating as well and have been monitoring it since but it just seems that the leaves get drier and drier - they don't come off easily though.
So I'm not sure exactly what else to do to help it - should I just continue to care for it regularly as I did, cut away the dried out zones, or anything else.
I'm also attaching a photo of it in it's current state.
Thanks in advance for any piece of advice.

Welcome to Empire.
It looks pretty bad, and dry; probably as you have guessed, a combination of heat and no watering.
Indoors heating systems leave the air very, very dry, which most plants hate anyway.
It can bounce back, but it's difficult to say. Water regularly, take all the fertilizers off, don't leave the temperature so high as they need some cold to rest, and pray.