The Taylor test reagents are the most accurate test chemicals on the market. The FC test is based on a drop-wise titration endpoint as opposed to others that use simple colorimetric matching. The color matching tests are much more error prone. The OTO ( yellow) test I have doesn't differentiate colors very well above 3ppm and only goes deep orange when my FC is above 8ppm. Taylor drops tell me my FC exactly to within 0.2ppm.

Long story short - toss out the cheapo test kits and use the Taylor results as authoritative.