>> Some of the ions are going to turn into colloidal over time.
I pretty sure that has something to do with it. Anyhow when I got the TDS meter I was told to test within a few minutes of cooking. Back then I made weak batches anyhow, more like 10PPM at the most so after a few hours of sitting those readings would come in as low as 4PPM.
Maybe after a few months that all changes around again… I don't test much these days just turn the SilverGen on high and forget about it.
I don't even mind yellow stuff since ozonating it clears that in one or two minutes.