Have you tried rearranging the tank decor? That may put them both on equal ground again. I also have a pbass and a dat, both are around 5-6 inches. The dat is slightly smaller but periodically chases the pbass around. Nothing serious, just some good old fashion Alpha male domination. I've heard of dats blinding pbass, so if the pbass is super passive and stressed you may want to seperate a bit longer. The dat will pick up on this "weakness" and hurt/kill the pbass.
shiii im gonna rearange the tank and do a water change but right now the bass is like attacking the glass? and his black strip is more like a gray now i think he is stressed when i leave the light on they dont fight at all but the bass is stressed. im really worried and i dont wanna sell/lose any of these fish
Hard to say without seeing exactly how bad the harrassing is... Got video?