Inconsistent KH/GH test results

• pH:
• Temp:
• KH: 5/8
• GH: 11/12
• NH4:
• NO2:
• NO3: 10
• PO4: 1
• Iron:
• Dosing: 15 mL Flourish, 1 ppm iron chelate, 3.75 ppm NO3, 0.6 ppm PO4, 0.5 tsp epsom salts, 4 tsp CaCl2
• NO3:PO4 Cumulative Dosing Ratio: 35.25:3.4 = 10.4

Notes:
I've been using the Red Sea brand for testing the KH and GH. I recently got the Aquarium Pharmaceuticals brand to replace the Red Sea tests, which were running out. When I ran both brands, I found that they differed:

Aquarium Pharmaceuticals: KH=8, GH=12
Red Sea: KH=5, GH=11

To be sure, I ran the tests several times. Which one is correct, especially for the KH?? Most people seems to think that all the KH/GH test brands will give accurate readings (versus others like nitrate/phosphate), but this clearly is not the case.

I like to experiment with the water the most just before the water change. I added a lot of CaCl2 and some MgSO4 to see if raising the hardness even more will help with the stunting. It appears that the heavy micro dosing doesn't seem to be having much effect so far.