Help me -My clones are dying before they root - I need a cloning video?

I use a clone dome with a heat mat .It holds 50 rockwool pucks. We have been using alcoho to sterilize tools and vita reow rooting liquid, then water in with b1. I am lucky to get 6 clones to live out of 30 they yellow and mold a waay. HELP. ME any ideas or videos would be appreciated