GH Test kit question

I keep getting this strange results from all of my GH test kits, which
I assume is due to extremely soft water, but I need confirmation from
you guys. I have FishDoc, Duplam, and Sera GH kits, all instructions
said that as soon as the test liquid turns green then it's done. Okay,
first drop, the colour is too light, I couldn't tell anything so I
continue to second drop, orange, third, orange... etc. I have tried 30
drops, and I still couldn't get it to turn green.

Is it possible that it actually turned green in the first drop, but
the concentration is so low that as soon as I put the second drop into
the tube the colour would turned back to orange? I am very sure that
the water isn't hard since my tonina is thriving.

Thanks
Kenneth