Increase the temperature of your hot water tanks. Many of us have turned down the temperature on our hot water tanks to save energy, however, this makes the environment for Legionella much more appealing.
Is this a ground water well? Did they treat the well itself or just the pipes?
Their drinking water needs really good filters or a small scale chlorinator.
We have discovered in hospitals and retirement homes there are usually small electric hot water heaters in individual rooms or in hand washing stations. These heaters have temperature mixing valves to stop scalding , usually set at 40 c , they were previously set at 60 c. the colder water allows the bugs to breed.