I've just put the rockwool into soak, the method i have used is the bath tub again. I ph'd the water to 4.5 and then used some liquid silicon. Liquid silicon has a high ph value, it is very alkaline. After adding the liquid silicon the ph came back to 5.5.
This is why I like to use liquid silicon in my hydro setup.
The silicon solution is a silicon supplement, supplies higher levels of potassium and silicon to build stronger plant cell walls, providing a barrier against piercing-sucking insects and invading fungi. Liquid silicon reduces disease and insect problems, increases stem strength and leaf positioning, which improves photosynthesis. It also increases heat, drought and cold tolerance. Use as a supplement with any fertilizer to provide non-toxic preventative protection against fungal infections and insect infestations. Recommended for all plants.