Update:
I never did figure out what was up with these two. I started to be convinced that maybe the marks were just damage from running into stuff before.
I had decided to slowly reduce salt levels (they were at 1 tbsp per gallon for months).
Two days ago, one of them looked paler and it seemed sluggish. Today it was dead when I woke up. I don't know if he died of stress from the salt, or from being dominated by the other Dority with him or maybe he was sick this whole time.
The one that died was the one with more noticeable marks. The surviving one just had one mark.
I guess my plan is to just slowly reduce the salt by water changes and then just see how he looks when I have zero salt in. I know he's getting stressed now being alone in the tank.
Im debating if I should out him with the 6 praecox in the other 10g if both tanks seem fine in a few weeks.
I examined the one that died. The marks don't appear to be any erosion as it felt smooth when I ran my finger over the area. Couldn't notice a difference in the feel of the marked area or regular looking areas. There didnt appear to be anything growing on lips or on marks.
I wonder if anything was even wrong with these guys or if it really was just marks from running into stuff like someone speculated on another forum.
Post mortem look at marks out of water.