It's an issue of the chelator, works okay....in softer low pH waters.
Even there though, I've noted as some rather asute scapers in our club after several years of experience, that the TMG gives a nicer sheen to leaves, crypts etc........it has a better pH optima for our tank's alk and pH(this is measured without CO2 injection).
I spoke with Alan today about the trace I am going to have made(more for my self, but may as well make some extra for the hobby and save them 10-20X off the name brands).
I have several things that I'll be using.
GH booster is nice because adding another 1-2 degrees of GH does not hurt or cause any issues with any plant. GH booster alos has K2SO4, so K i covered, and there's some Fe and Mn in there as well.
So you have K+, Ca, Mg all covered by one simple dosing.
Of course some might suggest K+ causes algae, or excess Ca or Mg.......but they need to prove it in a controlled system for all cases, not just their one tank etc.
You make a hypothesis, and want to argue for it, then you need to see if it's true or not.
Just like the legal profession, circumstantial evidence alone(correlation), does not cut it for proof.
I've done this and have never found any issues with a very wide range of plants species, wide species range of fish etc.
So it's a rather simple process, if these cause issues as many enjoy claiming, then why when I add them I do not have the same issues or response, instead I have nice plant and fish health?
It cannot be due to that.
Note, this does not say why the folks that made those claims are having issues however.
It only shows what it is not.