Two cories died over night. Pretty sure one was the one not doing too well....the other I NEVER found and I spent a long time looking. Removed all the decor and looked into the filter and all around the tank in case it got out of one of the two small openings...nothing. Theory is that the betta destroyed it over night. He was chasing them yesterday so I guess he escalated. Anyway, got a replacement for the one body I did have and got the betta a new, smaller tank. Its only 3.5 gallons, so not ideal, but its heated and has a filter as well as a live plant and cave. This way I can keep him and still have my community tank...and keep him healthy while I monitor the cories in case more drop dead/go missing. If they're still ok a week or two from now I'll get more for a little bit bigger school and get a slightly bigger school of tetras or danio than anticipated with him out of the tank.