My went out of town for 2 weeks and left me in care of his discus and I came home from work and 6 of the 8 are dead. I'm changing the water now, in hopes that the two that are alive will make it, but i don't even know what happened to make the others die. They were redish looking now they're brown. There was an automatic fish feeder attached to the tank, it fell in and when I tried to get it out with the net, food spilled all over the bottom of the tank. What should I do to keep these too alive?