are they sat in wet ground??if so thats the problem, broms dont like there roots to wet. the way i got around this is to get some bits of bog wood and put them on the floor and then plant the broms into them
By the looks of the pic you have a pup coming from it, am I right? Once they do that some speices will start to die.I'd cut it off and it may recover.I have some broms that are over 2 years old and when ever I see a pup I cut them off.They have produced alot of them for me.