Water changes yes! Source also confounding....
Are you dosing iodine? Perhaps a general trace elements additive? GFO? Any additives?
One could blame zinc and iron on metal in the tank somewhere (I think stainless has zinc) but the iodine feels like an outlier? Just more speculation, but seems like the metals in the tanks results have also included aluminum and tin in some of the results I've read. I think a general reef additive I used a while ago had zinc and iron.
i was dosing red sea's 4 part trace elements, one was iodine, followed directions to a T and it seems to still have been a little extra than what the tank needed. no GFO, but i have a Ti heater, just checked all of my pumps they were all in perfect condition. I saw 2 things that could be contributing to high levels of metals, one was a hose clamp that was in the water, it looked to be in great condition, but i removed it anyways, the other is part of the auto top off system i am running, it has a screw/nut that was just starting to rust, i will go to the hardware store and get some plastic ones to replace them. Other than that i am not sure where extra metal would be coming from, I did use some pliers in the tank a long while ago, but i seriously doubt that caused these elevated numbers.
My plan moving forward is to do a large water change and then check levels again in maybe 6 weeks or so.