Transplanting rockwool to soil-----

So I've read a bunch of threads about doing this and still had a couple questions. I aquired 3 plants, all about 2ft tall and 2ft wide. They were a grown on an ebb and flow in rockwool and were delivered with a small rockwool cube placed on a larger one. I placed these directly into roots organic soil, covered them, just a thin layer of dirt over the top of the cube and placed in 5 gallon buckets under a 400w hps. I want to take them into flowering asap, but want them to be completely out of shock before going into flowering. today is the third day i've had them, and they are starting to droop a bit. I watered them once after transplanting....but am wondering if I should be watering the rockwool to keep it moist, as I'm just going by weight of the bucket for watering now. Also, when should I first add nutes(using RO as well). They are all green and healthy, I just want to see them stretch towards the light:) Any advice here?
 
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