This week, I let her go on her own alone and stretch tremendously (~ 1-2 cm per day).
Still issues with pH and (I think) to many nutrients in the soil. But she takes it like a champ.
Day 45: Water 3l pH 5.7; 1400 µS/cm; Drain 0,5l pH 7,0 (!); 2000 µS/cm
Day 48: Water 3l pH 5.1; 1600 µS/cm; Drain 0,3l pH 7.1; 2200 µS/cm;
Will do a flush next week to pH adapt the soil and refill with nutrients.