GT3RS, I've seen incoming rain break the hypolimnium and roll anoxic water, killing CC and others but I don't "think" we are far enough into warm weather for that to be the case yet, but if you've fished hard with several live baits, hard baits and really give it an honest effort, one could say it is possible you have very few if any HBG or LMB left. In certain conditions, the old and very young are the ones to perish-first. I have a pond I manage that had a partial CC kill that we also lost over half of the SMB population and quite a batch of 4 yr old adult BG but when the smoke cleared we still had a fair number of fish the same size as those that died-survive. This was a cold rain event in a non aerated pond so several possibilities for the cause. Sometimes it's hard to find the exact reason.