I bought 10 fish yesterday and 7 of them have all died the same way. They swam under this particular rock in my aquarium and then they rush out of it and swim around the tank like crazy. Some of them look like they are dead after this and then two minutes later I can see their gills moving, and when I tried to get them out with the net, they started swimming around like nothing happened. Right now in my tank I have 1 yellow lab, 1 rhino pleco, and 1 electric blue hap. My tank is 100 gallons plus 20~ for the sump. I've tested the water multiple times and nothing seems out of the ordinary. Pease help.