I understand there are different variants of duboisi.
Bemba up North
Kigoma covers three collection sites, quite wide spread.
Karagao
Kobago,Helembe
and
Karilani.
They slowly lose the white spots as they get older. My guess is some have already lost the dots and others are still losing them.
Prob just a tank bred thing or a young fish thing from the usual mass produced duboisi. Who knows what variant these are or have in them? Now so far from wild prob imposible to guess. Not a desirable trait I guess. But it may not last, they may lose it as they get older.
While it has been known for just 8 to get on, I tend to recommend folk get more than this so if they get a male heavy group they at least get some to live together and breed.
Yep it seems likely that the one picking on the other is because both these two are male.
In such a small group you will be lucky to keep more than one male alive I think.
dubs are funny things not all agression is male to male. Females and males can fight as can two females so its for sure not a good way to sex them.
You need to vent them to be sure what sex they are.
All the best James