Jorges Cervantes has a great video on taking cuttings on youtube. It is the only video I have watched on cloning and I havn't had one fail yet. You seem to be doing things right from your description, although you say you "clean" your cuttings and I have never done this. One thing that might help improve your success rate is switching to rockwool cubes or peat plugs (I use rockwool cubes) but peatless soil should work just fine.

Other things to note...

I mist the inside of the dome not the cuttings.
The dome does not need cleaning daily.