5" is still a juvie ? At that size, he's still a baby when it all boils down to it. With every large, aggressive CA species I've kept (which is pretty extensive, and carpintis included), juvie fish go through various "fear periods" as I think of them at various times as they mature. They'll be super confident and outgoing for ages, and then suddenly they play shy and hide and spook at everything. Then they'll go back to confidence, and often hit another round of wussiness again later down the line. Literally every juvenile large CA cichlid I've ever kept has done this. They're still babies, small enough to potentially food to many others if they were wild, so I think it's just an instinctual part of their maturing process. Bruce may have been pushed into a fear period by your visitors and being a 5" juvie, could take a bit for him to bounce back to his previous confident self. As long as he's eating properly and otherwise looks healthy, I wouldn't worry about it. I'd advise giving him some more decor, a wide open space like your set up only makes a scared fish more skittish. More cover will make him feel more confident while he regains his ego. And adding some dithers may help, though options are limited in a 55. Giant danios are my go to and would be my recommendation...just make sure to QT before adding if you go that route so Bruce DOESN'T get sick.
