Hello fellow french person! French are rare on OB I noticed...Where are you from?
I'll jump in and give my
, for what it's worth. Why don't you buy some more bark to repot it? If you really want to do 100% Leca, make sure you have new roots growing, or else it's doomed from the start. If the roots are in bad shape you might have better luck with bark, and you can always put it in semi-hydro when it has recovered. I don't know much about semi hydro, but I don't think it raises the air humidity. I have my plants on humidity trays and have a small humidifier running part of the day.