I hope it's not Luck showing stress bars.

If so do you have a live barer trap? the sort that is plastic has holes in the bottom and floats at the surface. Maybe put him in one of those with a bit of weed and see if he loses the stress bars. That way if the other fish are stressing him he is sheltered from them and can get more accustomed to them through the plastic. It could always be something else that is causing him stress but isolating him while still in the same tank might reduce one of any number of factors.
If it's not Luck showing the stress, I hope Luck is still going strong in his tank with his fishy neighbors.