[Edward]

Plants don't care about KH and pH so fiddling with soda doesn't do anything beneficial. Also, to your post about red plants, plants are not red because of more Iron, more trace elements, more of so-called booster, more GH, more P and so on and so on. Real red plants are red no matter what as long as they get the basics what all plants need. Then there are plants that will turn red when stressed by low NO3, high light intensity or close to toxic chemical levels. Under strong MH lamps even Echinodorus tenellus grows reddish.
Plants prefer CaSO4, not CaCO3 from tap, so make sure you have 20 - 30 ppm of Ca by CaSO4 in the aquarium. Don't worry about KH and pH, no need to even test for it. I use zero KH water only and when substrate increases water KH over 2 dKH I lower it with water changes. Mg is taken care of by PPS-Pro dosing so no need to test or dose extra.

 

[Edward]

Plants love Ca from CaSO4 more then tap Ca from CaCO3, but most plants can still adapt to tap CaCO3. Dissolving CaSO4 in aquarium takes 30 minutes, but CaCO3 two days, make your choice. This does not have to be dosed daily which actually makes it worse for plants. Also, plants need so little Ca that it takes months to lower Ca from 30 to 20 ppm. PPS does not contain CaSO4 in any solution because it doesn't dissolve in small quantity of water. It has to be dosed in dry form if needed.