I have a bromine spa that I have just refilled and am balancing. I added Br concentrate and MPS. After a few days I tested my Bromine level with Taylors test kit using DPDpowder and R-0872. Then I tested with Taylors drop kits for OTO and DPDdrops (R-001 and R-002. My results varied widely!

DPD Powder and R-0872 7.5
DPD R-001/R-002 barely detectable

What's up?