I feel like a bit of a dick now, I hope you got the right kelp, they sell two kinds last I saw. One is a full fertiliser with kelp and one is a kelp tonic with no added NPK. Hope you got the later. If not you can always return it for a swap.
I don't want to be the cause of any further problems for ya like overferting..
Regarding what your hydro store guy said about microbes, I think he's right, as In they are ment for a medium they can live in and create a biosphere. Not sure if theres any value in adding them to rockwool on its own. I wanted to use them initially to unlock all those nutrients that get bonded to the coco. I suppose there a possibility they would have some benefit in rockwool as most bottled nutrients are not fully available to the roots. I might have to have a read up on that and see what I can find out.
Your gona have some serious amounts of buds when you get the new CMH set up man..