Cymbidium: new growths rot

[Annaswe]

Hi everyone!
First I want to apologize for any misspelled words since english is not my main language.

So, the problem then.. I had a no id cymbidium, bougt it with flowers and everything was fine until i repotted it. Then all the new growths start to rot from the inside (black, soft, non smelly) and eventually, even tho I cut away the infected areas and hydrogen peroxide the cut, it spread and the orchid died. So i bought a new one and (almost) the same thing is start to happening
A new growth has a black "hole" in the side of the base. I have clean it and hydrogen peroxide it. Why is this happening and what am I doing wrong? This cym has its own fan now and sits in a South facing window. Since i live in Sweden the sun wont burn it and it cant live outside atm cuz only bears and mooses can tolerate this shit weather...
The medium is a mix of medium bark, some spagh and perlite. When i repotted it, i hydrogen peroxide the roots and the roots were in good condition and almost non were damage. All of the old medium was thrown away.

Hoping that maybe one of You all know what im doing wrong, cuz im not ready to give up on cymbidiums yet <3

/anna

[Cym Ladye]

Why are you using hydrogen peroxide? If full strength it will severely damage new growth.

Aside from that, it appears that water has gotten into the new growths, failed to drain and they have rotted from black rot. Using good air circulation is important.
I do not know when you repotted your plants but spring is best as the growths are most active at that time. If you are spraying with water frequently, that is another cause of water not draining from the crowns.

Without more on your daily routine culture care, I can only make general assumptions and hope one fits the cause.

[estación seca]

It's cold and dark outside now in Sweden. What is the temperature in your house? Are you giving the plant any extra light?

As Cym Ladye wrote, cold and wet will rot new growths. It is also possible a snail was in the soil with your plant and ate the base of the plant, allowing infection to enter.

Cymbidiums can be difficult to grow in cold-winter climates. They take up a lot of room. They need very bright light when growing, so many people use artificial lighting in the winter. They like to be cooler than many people keep their house in the winter.