RO water has no KH, so you must add a buffer. Using a carbonate based buffer will not invalidate the CO2 chart. Most people will tell you to use baking soda. I prefer to use Seachem Alkaline Buffer, which is still basically baking soda, but it's crystallized (not powdered) and refined to remove small amounts of impurities so it doesn't cloud water. People often flame me for using it, but it's my preference.
For GH, I don't like RO right or Equilibrium because it contains large amounts of Potassium. Equilibrium (when dosed as instructed) will raise potassium to 20 ppm or greater. While many people say that's an optimum level, I like to control potassium levels separately. So for GH, I use Kent Botanica GH+. It's a liquid that contains a premix of only calcium and magnesium (which is what most GH test kits react to). Shake it up, add it, no clouding. Again, many people prefer to use "bulk" products like those sold at Greg Watson's, however, I like the ease of use of the Kent product.
To add potassium I dose Seachem Potassium.
I also dose Seachem Fresh Trace to add trace elements into the mix.
Flourish Excel really isn't meant to be added to RO water at a water change; it should be dosed daily per the instructed dosage rate. While it says you can use it without CO2 injection, very few plants will grow like they would with pressurized CO2. It works best when used with
Interesting tidbit on Flourish Excel... the main ingredient in it - a dialdehyde known as Glutaraldehyde
(Seachem lists it on the label as "polycycloglutaracetal"), is used as a disinfectant for virus, fungus, and bacteria in higher concentrations. Seachem also uses it in Stressguard and some of their medications such as Paraguard.