The CuLator doesn't always change color and it's slow. The key is whether you tested metals before adding the CuLator and have a lower tested metal content afterwards. Without the CuLator, you'd have to add the HEDP metal sequestrant periodically forever or at least until the water got sufficiently diluted.

That is strange that it took so long for the chlorine to hold. Even if you added too much ascorbic acid, the chlorine would react with it quickly so you should have been able to shock through it in a day or two. What you describe sounds more like what happens when someone uses an EDTA-based sequestrant/chelator since EDTA reacts with chlorine more quickly than HEDP and creates a noticeable chlorine demand.