Rowa is quite effective. My po4 was at 0.94 before, after replacing a new bottle, it dropped to 0.55 in one day. This is assuming you don't have anything in the tank that generate phosphate (e.g. something decaying, or old DSB that is leaching phosphate).
As for nitrate, i would suggest to go for Bio pellet or bio sphere. They are safest way to lower your nitrate compare to vinegar dosing.