FC water testing sample doesn't clear up

[comeuppins]

I am in the middle of a slam, raising my FC to 31(per swg pool math table). When I tested this morning my FC was 7.5 (i poured some bleach in last night). Anywho, using my k-2006 kit, and adding 4 jugs of bleach my sample was pink and as I added my drops of r-0871 (100+drops) I stopped bc the water sample was clearing but took on a very slightly brown color but never totally cleared. Using my initial sample this morning before the slam, the water sample cleared up just fine.(FC7.5) Why is this sample getting a tan/brown hue?? Is it metals? We have finished 3 days of heavy showers in our area as well.

 

[Texas Splash]

Perhaps you needed just a little more powder as noted here from the Extended Test Kit notes:

Using the small spoon shaped end of the dipper, add one heaping dipper, or two level dippers, of R-0870 and swirl to mix. If the sample turns pink for a moment and then turns clear again, or if it turns brown, add another dipper of R-0870. If the sample remains clear the entire time, your FC level is probably zero, however it is best to verify that with an OTO chlorine test, since the FAS-DPD test is prone to the occasional false zero.

FYI - Are you using the 10 ML sample? 10ML water, one "heaping" scoop of powder, then mix & count drops. Take number of drops to clear and divide by 2. Example: 20 drops = FC of 10.