Hi,
I have recently had the same issue. My nitrates and phosphates bottomed out. At first, I tried feeding more. then I tried Red Sea Reef Energy for a few weeks. i also started adding phyto. Nothing gave reliable results until I started dosing NeoNitro and NeoPhos. I still dose it and get a good dose response in that my nitrates and phosphates are reasonably predictable depending on how much i dose.
As my tank consumes the stuff, I have found that i need to dose well over the suggested label starting doses and the only way to dial them in was to dose and test daily for a while. This was a great confirmation of the 'only dose what you can test' principle for me. i am still feeding heavily but not counting on feeding to keep my parameters in check.
Best of luck!