If you find a seeding or a plant is is very weak, it is very likely that the roots is rotten.
How to deal with the rotten root.
Firstly, you take the clivia out of the pot, and remove all the rotten root. Then you use the potassium permanganate to sterilize the root and dry the root.
Secondly, breed the clivia into the new soil.
If the roots are rotten very seriously, please mix proper sands to the new soil.
Rotten more seriously, mix more sands to the new soil.
If hardly roots survive, you need mix lots of sands to the new soil. The proportion is: Sands 80% and soil 20%.
And when you breed the clivia into new mixed soil, please be careful and light. Please dont damage the remainder roots.