Lemon fin barbs aggressive?

[Longfindragon]

I have 3 lemon fin barbs that I've had for four months now, they do stick together but usually harassing each other nipping and bullying. 1 in particular seems to be the culprit ( the biggest) is this normal for them?
They're about 6 /8 inches and in an 80g tank for now along with 3 pink tail chalceus' and an iridescent shark. Tank has a fair amount of flow (15xtank turn over an hr.)
I'd let them be but I'm worried because they all have nipped fins (except the bully of course.)

 

[Deadliestviper7]

With the more agresive barbs u want a group or 6 or more to reduce agression , also add visual Barrie's such as plants

 

[ichthusfish]

numbers do the trick