I hope someone knows....my first tank, 50-55 gallon freshwater, did all the testing, etc, got 2 electric blue jack dempsey's, everything was fine, they were lil, about 4" long, i guess, feeding them flakes, 2 1/2 weeks later, i got a female convict and a firemouth, all the same size. well, there was a lil bullying ech other, but one of the dempsey's just shut it down, WOULD NOT EAT, just looked at the back wall, always by the filter or the heater or in the corner. so i check the ph, did a water change, he just wouldn't eat or stop looking at the wall. the others would pick on him but he would just swim off, get away from them and then go right back to his walls. And wouldn't EAT. his color wasn't vibrant anymore, he was pale while the other one is bright blue, black when he's hungary...beautiful....yesterday i got home from work and i couldn't find him in his usual spots he was on the dead. and i have no idea why? PLEASE HELP