Orthophosphate is inorganic...it's a very stable version...organic phosphate is often reduced to the ortho to measure it. The Hanna (nor any hobbyist) test kit do not reduce organic phosphates to ortho or "free version" to measure it. Either way, you're missing out all organic phosphate that's may be available to life (or algae/corals) but not the test kit.
I would toss the tests and check algae on the glass.
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