Help! Alocasia in LECA

In the summertime, up until autumn everything was great, this plant was thriving in LECA, but now poor thing looks awful. Lately I haven’t fertilized it (thinking that I should not do that in the cold season). The leaves all have turned yellow and brown and I just cut them off. What might be the root cause of the discoloration? I see one seemingly rotten brown root in the LECA underneath, should I have removed that to avoid all this? Thanks for your help!