Welcome to Pond Boss, Jimbo!
It sounds like you have the classic problem many of us have with LMB ponds--stunted predators.
The experts can help you figure out why you have a yearly fish kill, but it sounds like problem #1 is a lot of jaws to feed and not much forage to go around.
When you say that the pond was "barren of fish and had the richest assortment of critters I had ever seen," what exactly do you mean? Was there any forage in the pond prior to stocking SMB [either baitfish of some sort or another reliable source]?
