Hmmm. Well theres not a whole lot to go from then. Unless it's just a freak thing I would be very watchful of my fish though. How big is your BOW? If it's not to big and you have less water in it then ever before??? You could have a start of a D.O. issue? Like you said I would be mindful of any bigger fish coming up to the surface. And if you can get a basic water test kit from a local place there and test your water. A simple dip strip would be better then nothing at least it would tell you where you stand on PH and Nitrates and Nitrites and such. I would take a few readings in different spots your PH should be around the 6.4 to 7.3 range if it comes up really low like 5 or under or really high like 8.5 that could be a reason for the younger dead fish. Or you could have had a big swing in PH at some point and that is why the fish are dying? A lot of maybes for sure! Let us know if you find anything out.

The only difference between a rut and a Grave is the depth. So get up get out of that rut and get moving!! Time to work!!