Add Microbebrew/ Kangaroots now?

I have 2 seedling that are 8 days old today in my DWC. I just transplanted them last night. I'm using just plain ph'd chlorine/chlomide removed water at the moment. Now I know I cant feed them any nutes until another 6 days or another set of leaves. But I was wondering if I can add the Foxfarm Microbebrew or/and Kangaroots to my res since both are supposed to help or increase root mass development. The reason being is that I read that the plugs already come with beneficial microbes in them so I'm thinking this would only help. I also have some Superthrive but I am scared of using it. I only used it in the glass when I soaked the seeds before putting them in the rapid rooter plugs. One of the plants is GHS Bubba Kush and the other is BB Blue cheese.

I am not familiar with those products, but I am familiar with using microbes in a DWC. You can use microbe products from day one. They Will help your roots reach their full potential faster while also warding off disease.