Solo, I wouldn’t worry about your runoff ppm as much as you are. You are in soil, as the water movement through the soil it will pick up the small soil particles and that will be coming out with your runoff. I typically run everything organic and when I do I never use meters; they do not work correctly with organic nutrients. Both tds and pH meters base their readings off the charges of the particles in solution. Lots of organic materials have neutral charges and will not be read correctly by the meters. Also if you end up with soil particles in your runoff you will never have an accurate reading of what is actually coming out compared to what was going in. To me it I see all about using nutrients in moderation, I almost never go full recommended strength, and watching for what’s the plants tell you they want. But all in all I think you have done a great job with this grow. As you gain more experience you will only grow better herb. I am looking forward to seeing your future grows.