I'm excited to see how this system grows! I'd say your algae is probably soaking up any nutrients that would show up on your test so I would say your test kits aren't inaccurate. Did you have your t5's on while you where cycling before you added corals? If so, algae might have got a foot hold before anything else could. Maybe taking all your corals out and turning off the lights for a few days might help, hopefully. I'd really like to see this thrive.