I suggest that you ignore Seachem's recommendation for dosing 5 ml/10 gallon of Excel when large water changes are done. It has been demonstrated that all this accomplishes is to stop the growth, if not kill vals, and a few other plants. Excel lasts about a day in the aquarium before it is deteriorated, so dosing that big "starter" dose affects only that first day. Far better is to dose the 1 ml/10 gallons, or 2 ml/10 gallons, every day. I found that dosing 2 ml greatly improved the growth rate of plants in my low light tank, without harming the vals.
You shouldn't have any nitrite in the water. 5 ppm is much too much, and may indicate an incomplete nitrogen cycle.
I don't know what size your tank is, but even one tsp of Equillibrium or equivalent in a 55 gallon tank at each water change will not increase the GH enough to be a problem. 40 ppm of nitrates is not way too high. It is about as high as you should ever go, but many people keep the nitrate that high without obvious problems.