Plants don't take up P as fast as they take up N which is why the recommended ratio is 10 to 1. If you have a source of P in your substrate, it's possible that as it is drawn from the water column more is being liberated from the substrate. Assuming your test kits are good, keep testing and let us know what you see.
Aquascape? I'm a crypt farmer.
It's a fine line between fishing and standing on the shore looking like an idiot.
That IS an aquascape, it's titled "The Vacant Lot".