I think it's at least partly bullying; they need larger numbers and more females than males. I started with 8 spotted blue eye rainbows, 3 males and the rest female; the 3 males harrassed the females to death and now with just 3 males left two of them have bullied the third so much his fins are torn and he's very thin; I've had to try to separate him out for a while. I suspect something similar is going on with yours.
The white spots are a bit of a concern though; does it loook like ich or like his fins have been nipped? If it's ich you'll have to treat the whole tank (slowly raising the temp to 86 over the course of a day or two should treat it, leave it at that temp for about two weeks and increase water changes with substrate vacuum to every couple of days). You could also buy a breeder net and put the sick one in it to separate him out a bit from the others so he gets a rest . Also try increasing the numbers of males and females if you have the room. You could try to rearrange decor a bit as well to mess up territories. It's likely the first male has territory in the tank and he feels the new one is threatening him.
The white spots are a bit of a concern though; does it loook like ich or like his fins have been nipped? If it's ich you'll have to treat the whole tank (slowly raising the temp to 86 over the course of a day or two should treat it, leave it at that temp for about two weeks and increase water changes with substrate vacuum to every couple of days). You could also buy a breeder net and put the sick one in it to separate him out a bit from the others so he gets a rest . Also try increasing the numbers of males and females if you have the room. You could try to rearrange decor a bit as well to mess up territories. It's likely the first male has territory in the tank and he feels the new one is threatening him.
