the flowerhorns seem to be fairing better then the others in that tank so far. however i must recommend against this for anyone.
it's only been 20days since you put all these fish together?
most fish will take at least this long to acclimate to their new environments.
like was stated before, it's only a matter of time before carnage in such a environment.
many different scenarios can come into play. i think you did do good with decision to not add decor. decor promotes territories. thus will promote defense of said territories.
if something does pair up in there. you'd better make haste to remove the others before they get killed.
good luck with your fish. i hope everything works out for you.