The fact that you never changed the water and fed quite a few large predators with nothing but high protein food is probably where the problem originated from. As far as I know, HITH is caused by prolonged exposure to poor quality water compromising the fish's immune system and allowing an opportunisitic parasite to 'dig in'. It is fatal if left untreated, though I've never personally seen a fish pull through it completely. It's also very common in large cichlids.
Do what the guys have suggested. Change the water, or some water, warm them up and feed them vitamin enriched foods.
Do what the guys have suggested. Change the water, or some water, warm them up and feed them vitamin enriched foods.
