Although a little less newbie than you. Chas' Law is that you should drain after 1 month of usage and start fresh.
But since you have Iron/Manganese in well water, this may be where the color is comming from. You don't say anything about treating the water for it. Everything I've read states to add some "metal gone" product when you add water. (Sorry, I don't have a metal in the water problem).
You need to get off test strips and pick up a Taylor Test Kit. As far as PH/TA, worry about PH, this is more important IMO. Also, high sanitizer can alter any reading, so make sure your sanitizer is not in "shock" mode.
Other than that, I would say that the cheapest, quickest and best chemical would be water.
I hope this helps!