heres a calculator for Ryznar/Langelier Indeces which measure saturation at specific ph's. You can have water of high pH still being corrosive based upon its RTW indices. This site is the AMerican WAter Works site . These guys are miunicipal water engineers and are the last word on quality maintenance and use of water treatment. SInce they represent users they are like you, a cutomer of water treatment , not purveyors. H2O man is the correct answer--find out whats the makeup of your water before you start throwing specific treatment at it.
Since your problem is obviously being masked by dissolved Oxidized iron, we dont know whethre youve got a MANGAnese problem, which has a health index based upon dose equivalents for kids. ALso the concern for whether your well pH is 6.7 BEFORE it buffers out all the iron. Remember an acid water will buffer itself on whatevers available and iron or Calcium are specific cations that are great buffers.
Is your well in sand formations or hard rock? If hard igneous or metamorphic rock (or sandstones) chances are the pH is closer to 5.8 to 6.5 and your actually getting dissolved iron from the formation at the well bore , or in many cases, the well casing itself. Open your well and look at the casing, is it all corroded or does it look smooth ? If you can see a change in pitting right at the water level , then your water system has an aggressive and corrosive index
CORROSIVITY INDEX CALCULATOR , by AWWA