In central Tx. on a 1.5 acre tank we have a similar problem. We caught about a 7-8 lb. bass two years ago on a minnow and have caught some 5 lb's since, but nothing larger. The water cleared not too long ago and we could see the larger bass but they would not bite. I think the Florida strain is a bit more adaptable and since then I moved some natives from another tank to that tank and have had better bites from the Florida strain fish but still have not equalled the big boy. I think lures are history once successful and only live bait will work when stealthily presented. They are probably still there.