Lemme guess Harrison's?

There might be a few FHM hanging on, but it's unlikely there are many..It could even be a simple missed identification of species if they are pretty small.

If you added HBG, they are a cross between BG and GSF and could just be a regressed offspring. It is more likely they came in the original fish stocking.

There is no benefit to adding HBG to a pond with BG and can be some real downside to it, regardless, it is done now and you will manage for that.

Your Crappie can pose some management nightmares also in a small body of water, so you'll want to learn how to look for issues there as well. A boom spawn of Crappie could even explain FHA surviving if the BC are munching down all your LMB hatch. If you start catching lots of 6'10" BC and few 10"+ LMB, you may be well on your way to a BC overpopulation already.