It sounds like to me that there was some toxic elements that came from your well water. It is definitely not normal to find dead fish especially if you are finding them regularly something is happening to them. I have been managing a 1 acre pond for 6 years now and stocked it heavily the first 3 years and have been stocking it heavily with bait fish ever since and I have never not a single time found a dead fish. Fish obviously do die but it shouldn�t be happening regularly the fish in the pond should be getting eaten by other fish long before it just dies IMO. That being said it doesn�t mean that your source of water isn�t the end of the world if you have no other options you can probably still manage a decent BOW. Maybe consider adding catfish to help clean up the fish that can�t take the toxins. Over time the fish that can handle the toxins well will breed and produce more fish that are likely to be less susceptible to the toxins in the water. Ideally getting a new source or aerating your water before it goes in the pond to help remove harmful toxins would be the best option but if not you can make do with what you have if need be.