Sounds like to me you have this fish 'stressed' for some reason AND you have other fish that are overly 'shy', and hide a lot? Have you considered that perhaps one of the fish in your tank is kickin' the hell out of the rest of em when you're not looking? Like maybe at night or something? You wouldn't by chance happen to have a fish that just stays up in the top corner of your tank most of the time it's so "shy" would you? Cause that's not shyness. That's terror...
And do you perhaps work a lot, and you only see the fish in the morning when you feed them, and late at night when you get back home from work? You barely have time to feed em and do a small water change every other week or so? It happens, we all have lives. In that case, maybe there's more aggression going on in that tank than you realize? Maybe it's just me, but I just got the impression from quickly reading through the discussion that there was a single bruiser in that tank whooping a bunch of peaceful fish into total submission. That does tend to happen to Severum's doesn't it?