Just curious...are you using the tiny little end of the blue scoop to measure the R-0870 powder? I don't know when you got your TF100 kit but if it was just this season it seems like you ran out of power too quickly. You should get 100+ tests easily.
Have you seen the TF100 test kit video for the chlorine test?
FAS/DPD Chlorine test for the TF-100 - YouTube
Photo below shows the scoop as provided in the TF100 kits but the container type and size is different so don't let that confuse you. We've had people here accidentally using the paddle end to measure the powder.