Do you have some CYA left? You could mix a rough reference sample to run a sanity check with your reagent.
The measuring spoon for the DPD powder might be a good size for that. Not sure about the exact dimensions of the Taylor spoon, but the spoon that came with my Australian Clear Choice Labs kit is 0.05ml. A spoonful of CYA should be about 0.05g to 0.1g, depending how heaped it is. Dissolve that in 1l of water (give it a day to fully dissolve), and you should have a "standard" sample of about 50-100ppm. That should be good enough to verify that your batch of R0013 is OK.
I assume that you verified back then that after adding CYA you really ended up where PoolMath told you you'd get to. Not that the CYA you added was a dud, rather than the test reagent...