i use a few things when cloning and superthrive is one of them.
i mix a seedling nute at EC1.0 or 500-700ppm add a few drops of superthrive, some trichoderma powder, cut my clone at a 45degree angle strip off a few nodes scrape the stem, dip into clonex then into some powdered mycorrhizal fungi then plant into medium and dome them.
The greenish algae you described is from light on the rockwool. H2o2 or a plastic cover on top will cure this.
J