Hey @ricky_simples i visited the jacks web page today. Do you have any info or knowledge of there water testing service? It sounds like a kit that they provide but i do not see it anywhere on the site for sale. The instruction forms makes it sound like there is a kit but i do not see it anywhere.Yes. I have a buddy who's just wrapping up his first grow using Jacks 321 and Happy Frog soil. But know that soil has nutrition in it, unlike coco which is inert. This means that you probably wont need to feed as often in soil, and a when you do it will be at a lesser strength than you would with coco.
If I was growing in soil containers using Happy Frog or Ocean Forest, I'd feed with straight water for the first month or so.