You are on the right track, but you're working in reverse.
To simplify things, I recommend mixing your source water to the parameters that you want the tank to be. Example, you've determined you want the tank to be 8dGH and 2dKH, so you need to test source water. If source water was 6dGH, and you want 8dGH, then add the appropriate dose of Equilibrium to the source water that raises it 2dGH. Same with KH. Then by doing water changes, you adjust the tank parameters to the source water.
When fertilizing, you want to dose enough. And by enough, I mean an amount that plants always have access to, with out depleting it to zero, and not so much to hinder plant growth.
You seem to be adding things with no specific goal in mind. I know that Equilibrium has Ca, Mg, K and Fe, but I don't know how much. Same with the root tabs. What ppm is in a root tab, and what nutrients are in them as well?
When our nutrient parameters are fluctuating our plants will suffer. This is why we want to know what is being dosed and be consistent with that dosing.
My best advice is to research what each of those fertilizers is adding to your tank(ppm). And set a per week ppm goal. A good starting point might look like:
7ppm NO3
1ppm PO4
10-15ppm K
.1-.9ppm Fe
Additionally, I would go really light on root tabs. Personally, I don't use them, but they can fill in the gaps.
I would find a more comprehensive fertilizer, Flourish is just a supplement. Choose something like Easy Green. Equilibrium and Easy Green should mesh well.
And the ppm is available to us with Easy Green. But certainly, there are other "all in one" options mixed in different ratios.
MC Cuba is a high light high CO2 plant. Don't get too upset it's not doing well.
Learn/Understand GH and KH, ignore pH. Understand nutrient PPM and how to calculate nutrient PPM when dosing. Once I was familiar with these few things, the tank got easier to figure out.
Light also drives all uptake, try reducing light intensity or photo period. 8 hours is plenty.
Hopefully I didn't bore you ☺️