Well, at the moment, the rotting is slow, at least for the moment, and some roots have poped up here and there.
My thoughts are that it may be excessive minerals and nutrients of certain types, namely due to the kitty litter substrate which varies considerably in minerals and nutrients. Or maybe the daily liquid fertiliser, or the tablet fertiliser.
Well, thanks for the help. I think I will have to hope it survives, otherwise cut my losses.