Yes that would be to many CC for BOD and carrying capacity when grown (2 lbs). At 1/2 lb each and 10 inches they should not have been the cause. The CC plus the FH would only be about only about 400 lbs per acre and with aeration should be no problem. The growing O2 demand by the CC plus reduced O2 production from plankton elimination in conjunction with the big BOD increase from dead plankton and FA is the likely cause.

One positive note - your pond has indicated its max productivity (carrying capacity) as currently configured at my guess 400 lbs of fish per acre. Stock the pond so that you meet your goals at under 400 lbs per acre when the fish are grown. As Shawn notes if you try to get to close to max lbs you greatly increase the risks of problems.