My guess is diet. They've been with loach varieties and other bichir growouts. Those fishes didn't have any issues. I've been feeding frozen tilapia primarily and these Indos starting having issues of being grounded (swimming but immediately sinking and staying on the bottom). There's 8 Indos ranging 3"-7". The biggest one solely has the forehead bump and lay on its side. Haven't seen any pimples or bump /boils. I will say a few a couple weeks ago had Popeyes on one side. That's all fine now after treating with rock salt and Epsom.