The FAS-DPD testing that was sold with Ben's kit will test chlorine up to 50+ ppm. If you're using OTO, then it probably is bleaching out. I can't imagine that much chlorine in one pool being used up that quickly, even with a big chlorine demand due to ammonia that is often produced when CYA is degraded over the winter, like Watermom said in her above post. Go ahead and run your test with the powder and drops--that one is WAY more capable of testing high chlorine levels than any of the others.

If you have high CC, that's another indication that your CYA was degraded into ammonia and will help us better figure out how to advise you.