what do you soak your rockwool cubes in?

what do you guys use to soak your rockwool cubes in (besides cloning solution obviously)

i had three ideas

1.) superthrive (1-2drops a gallon)
2.) would any additive that helps rapid root growth?
3.) light solution from my foxfarm trio?
4.)liquid karma solution??

last time i did my clones i just used water and they rooted in like a week..but any tips/advice anybody would like to share?

Straight water, pH at 5.5 - 5.9 for cloning.
I use lemon juice to bring the pH down to those numbers