Sorry about your loss...I'm A new guy here and although I only own one bichir i can say with much certainty that those fish look like they have columnaris. I lost numerous SA/CA cihlids in one afternoon due to it. it's extremely prevalent in temps over 78 and can kill otherwise healthy looking fish in a couple of hours. despite the fact that bichirs like warm water i would try for 75 degrees farenheit and hit the tank with a dose of Prazipro. (Prazipro is actually for internal and external parasites but for whatever reason does effectively treat columnaris). Best of luck with it.