three things spring to mind..
1) fish pick on weakened fish... I has a bunch on mountain minnows picking at a goldfish many years ago.. couldn't figure it out, but then the goldfish showed signs of illness, and the fish had been picking at his excess slime coat...
this would happen in the wild...
2) Lack of territories, you have very little rock in there currently, so none of the fish have defined territories... this was different when you had loads of rock in there... and there was never any aggression
3) Hunger.. without the live rock there is limited life in the tank, apart from waht you feed. I'm assuming you refuced feeding whilst in hypo, or at least whilst cycling.. but as the fish were stressed they had more things to worry than any of the above or hunger.. now they are relaxed and hungry...
maybe Elvis is an easy target...
I have to say Stars is by far the most timid of all my fish, and oddly stars and stripes are reknowned for it... stars will not rush for food but hang back whilst the other dive in.. i wory about him not eating and am working on getting him to hand feed so i can make sure he's getting enough food...
my banner fish will swim past and stars will shy away, even though stars is bigger...
Maybe see if you can work on the issues raised, one by one.. see if you get any results before rehoming everybody.
I don't see why they would 'suddenly' strat picking on him, i don't think fish have school yard fights like that...

