Besides placement, temp, lighting, and current, go get a good set of test kit like Salifert, you will then know where goes wrong with higher accurate reading.
Looking at the amount of fish, likely due to high nitrate. What No3 test kit u using? I think Salifert cost below $30.
For nitrate, you can look into biopellets, denitrator, refugium, water change etc.. I don't think you need a calcium reactor unless u are into sps, cheaper and simpler to dose calcium for Lps.