I've got 11GH and 6KH.
Is there value in still dosing Equilibrium after a water change?
GH is the measure of the amount of calcium and/or magnesium in water.
GH 11 is already high but it's still possible it's short of calcium or magnesium.
I wouldn't use Equilibrium because it contains both (and more of other
minerals) and would raise the GH even further with the substance I don't need.
I would see the water report or find a way to test if it lacks one or another.
Then dose just that.