The service lines may be copper as there are 0.03mg/L of Cu which is 3x more than the Fe. There's also a lot of Na, Cl, sulfate in your water. Doing large WCs just replenishes these nutrients, not get rid of them. This is one problem with large water changes.
Ideally, K>Na. I don't know what effects K<Na has on plant health but it's detrimental to many crop plants. This is something I'll probably experiment on after I figure out the necessary micronutrient ratios necessary to keep a tank healthy. If you really want control, using distilled water may be your best option if you have a solar distiller, or an RO/DI unit to reduce the contaminants in the tap.
Last edited by Solcielo lawrencia; 07-14-2016 at 07:18 PM.