I think you are absolutely correct, Grz. I noticed the same effect on a smaller scale back when I was living large and had a big backyard swimming pool to take care off. Once the algae takes blooms you can't simply clean the pool up to the point where it would not have gotten algae in order to get rid of what is there.
An anology in human health might be someone who eats a crappy diet that undernourishes themselves, smokes, exposes themselves to toxins, etc., and develops cancer. Adopting a healthy enough diet and lifestyle only to the point of where they might not have gotten cancer is not going to be nearly enough in most instances to beat the cancer.