sickly cactus

This cactus produced 5 sickly cactus "dragon" fruit that died & fell off before mature last year.  The far left branch shot up the wall about 8' off the ground.  My wife had me chop it off & it immediately shot off 2 more 12" branches.   My neighbors plant is twice as thick and produces 12 or more healthy dragon fruits.  Will post photo of his next & request suggestions.