Dead fish? (and fishing)

Just got back from 4 days of fishing at Lake Erie and wow was it tough.Caught 20 fish in the 4 days and they all came Thursday and Friday evenings on blade baits on the edges of the reefs. Did see one boat both nights putting the wood to em but no one else that we saw or heard of did well.
Does anyone know what happened to all the dead walleye that are all over the lake and shoreline, we had over 100 dead ones just on a 100 yard stretch of beach where we were and saw tons of them in the lake. All the dead fish are walleye did not see any other kind of fish.I hope some one has put an end to our fun.