Avacado plant still browning

Not long ago I posted my avacado plant leaves were browning even the new growth, like they curled and browned. I wondered if it was a salt problem so got soil for seeds/cuttings, I moved location to a cooler area in my house as it’s only small still about 10cm/15cm. However the problem still exists. Currently it only has about 3 leaves on it as I keep taking the dark browned leaves of. Any ideas what I’m doing wrong?