We have the same problem! I assumed I had damaged the other trunks somehow when planting it in a bigger pot but all but one of the trunks has died. These older dead ones are definitely dead but as they are entwined with the living one and are supporting it I have left them. I read somewhere that you have to let the soil dry before soaking it- a good water less frequently can be better than a frequent sprinkle, if that makes sense. Have you tried feeding it with plant food? I use baby bio and it seems to perk up then.