Purple cake purple punch X wedding cake

Purple cake Ok running into huge problems with this grow huge selections of the plant died it looks as if the branch’s lost Circulation the cages that I used are rusty I don’t no if when the plant grew up against the cage that had something to do with it or a root problem both sides of the plant are doing great but the hole center of the plant wept and died so I removed the Dead branches still a lot of plant there but it has taken a hard hit with this issue