Pictures:

Hello Yazan87,

What a lush plant! Makes me daydream about gardenias....

I am no expert, but I suspect the cooler weather may have brought increased fugal activity in the root zone as the soil doesn't dry up as fast. Do a check on the soil and make sure it isn't too wet. Let it dry a little between watering (but not entirely dry).

Again, this is what I suspect, I could be wrong.
Good luck.
Dar

did you add fertilizer? the brown leaf can indicate a burn from fertilizers or over water ?
is you pot well drain?

Looks like you may be over watering it and its in a tizzy because it doesn't like lower light levels.
Mine started to turn brown, but that was because I wasn't watering it enough (I've got it close to a wall mounted heater and it dries out my plants super fast!). I noticed that the new leaves would start to wilt. But if you are watering them too much, that will help turn them brown also. I would definitely not fertilize it in the winter, as it can cause brown patches on the leaves. Heck just looking at it wrong can do that! Don't let it sense your fear, or it will do other things as well that will make you worry even more. I noticed that when I didn't water mine enough the lower leaves would turn yellow, then brown and then fall off, making it look more like a palm tree with no leaves at the bottom. I'm wondering if you are over watering it too much? It could also be the shifting light levels too. We have ours under lights and in a south facing window, and it seems to like it there, even if the heater makes it use water up fast. At least then I'm not drowning the plant! Otherwise your plant looks great!

Hey Merciepoo!!!:-))))

Yaz: Please explain your watering practices, how often you fertilize, what kind of soil it's in and how much light it gets? The more detail the better to diagnose>

I am having a feeling that is salt burn related to a poor soil mix and bad watering/fertilizing practices. But with extra detail I will not be able to be able to make a complete determination.

Mike:-)

Dear All,

I am sorry I did not reply quickly.
Thank you very much for your replies.

My plant is almost dead now, less than 10% of the leaves remained with many burnt stems.

I have been told that it was because of too much water, but I changed the soil, and I reduced the water supply.

I used to put water every 3-4 days, and i believe it was excess.

I used some biostimulant to make it jump start again, but the problem is that no enough light is available here because of winter.

Next to the windows it is very cold with weak light, so I am relying on artificial room light.

Some new leaves are growing but at the same time some of them are turning brown then black directly.

I really hope it can make it until spring.

The location does not have enough light; and you cannot change soil for them. They will not survive this "trauma". Gardenia is quite difficult to keep, I think everyone agrees.