Using the instructions that came with the apfuk starter kit as that is what most people recommended, no co2 or l/c, all details are in my tank thread.
In that case you won't be dosing 1.6ppm iron, you'll be at roughly 0.5ppm, so that's a test kit error. To be fair you shouldn't even need to be dosing full EI in a low tech tank. Given your hard water, your pH is likely to be well above 7, so the EDTA chelated iron in the APFUK mix is likely breaking down too rapidly. I have hard water, and have the same issue in my low tech tap water tank.
There are two things you can do to help:
1) Buy some DTPA chelated iron - you can buy this in powdered form (Amazon, eBay), or pre-mixed in TNC Iron AT. You shouldn't need to add much, so I would keep it less than a 0.25ppm per week dose of that to your tank, so add it to your dosing container in sufficient quantity to achieve that.
2) If you are on an auto-doser, there is no real need to use alternate day dosing - that system was design to make it easy for people manually dosing. I would in fact perform daily dosing of both micros and macros. DTPA Iron breaks down when exposed to light, so dose your micros at night, and your macros just before lights on.
Give it a month or two and see how you go.