I have been cloning using the same system as reggerican's method with great results. I would suggest
not using a humidity dome if you're using rockwool cubes. I don't use one and get at least a 90% success rate.
The trick is to keep the under-side of rockwool slightly moist and warm.
A rockwool cube completely soaked generally weighs 25 grams. You want to shake out the water so that it weighs closer to 5 grams for the oxygen level to be optimum. Spray the underside once or twice daily to maintain moisture level.
I simply place on a heating matt that you get at local grow shop. If they start to look droopy, they need a spray of water on the bottom (not the top leafs}. I have also placed the tray of clones on top of shop flourecent light or refrigerator which runs slightly warm for same effect.
Just so happens that I have some recent clones I just took pics of. these are about 2 and a half weeks from having been cut from moms.
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Hope this helps.