man I can't believe my discus can do this.

I bought three bristle noses and put them in my 6 ft community tank that's got 14 juvi discus. I noticed that they were kindda picking on them but I didn't give it much thought. the next day, the bristles were dead, all of them and the discus were still biting them. To the point that the bristles were like kindda shredded. Don't think they have lack of food. I feed them with BW in the morning and they get 3 serves of dry food in the day followed by BH at night. What gives?? Does anyone's fish behave like that?

cheers
daz