My reds have always seemed mighty fine:
Low NO3 is rather a simple modification to PPS or EI, you simply add less to your tank/solutions
Why is that difficult?
A good test kit and a good calibration will also help.
However, while I and Steve Dixton showed folks a decade ago the color variation due to lowering NO3, as well as myself showing evidence in research, see Dave Spencer (out here at the UCD lab), I've had little issues getting awesome coloration from my plants using EI and good GH's and traces.
These pics have high light also, but there's no mention of that when folks discuss this issue, even still, at 40% less light, I still had decent color, see the top photo.
Redder is not better either.
I'm not sure why many assume that and why there is such a quest for it as well. Many tanks have too much red.
You can also change a lot by simply changing the bulb types as well, what appears red to you... can help. Some like the 9325K+ 8800K+ 6700K ranges, I like the Tritons from the old days, but like the above lights as well, generally mixing a 10000K to 6700K range bulb or mix of the other two.
Point is, I'd not obsess too much over the lowering of NO3. You can reduce the dosing easy enough, EI was never meant to written in stone(I've never said it ever was) and folks with high NO3 in their tap do not assume they still need to add the suggested KNO3 dosing.
Common sense does apply no matter what method you chose.