Iron can be important to a reef but not for corals, let be clear that every test on iron comes out always to 0.0.
You might think huh.......... why??
Simply cause the iron level in NSW is 0.000006 ppm, that said we really can't measure that with our home test kits.
So what your dosing is always way to much, maybe 100x the max limit of your tank volume.
Read up this article and do understand about iron.
http://www.advancedaquarist.com/2002/8/chemistry
Now dosing K and I can be important but only if you know where your numbers are.
If a chart is telling you that your levels are low, you need to ask your self how low in order to know how much you need to dose.