So, I thought I had been maintaining the 115g in a successful manner. Regular water changes and filter cleaning and a continuous water drip. With the removal of the plants I had started siphoning the sand too. When I lost 2 of the Tropheus I thought it was due to aggression so I moved them to the 90g and the shellies, calvus, regani and s. multipunctatus to the 115g. Life got busy so I wasn't spending as much time in the fish room. I noticed some heavy breathing a week ago so I did a large water change and removed 75% of the sand. The next few days I removed the bodies of the gold calvus, the adult female regani and a couple shellies. A few days later I had to euthanize my adult male regani as he was no longer able to swim correctly or maintain position against the current in the tank. I also removed the rest of the sand and added 20lbs of aragonite. I'm down to a dozen adult multies now and a few juveniles. There is one 2in juvenile regani left.
I think there was more waste mixed into the sand than I realized and that the water quality crashed. I tested water quality 2-3 days ago and last night and nitrates are <20ppm and Ph ~8.2. I will retest this evening for ammonia, nitrite and nitrate.
With the population density being so low now I moved a pair of Sumbu dwarves from the 55g to see how the extra space in the 55g would effect the pecking order. The colony is now 3 males and 2 females in the 55g.