Best medium after seeds crack

What is the best way to start seeds on the road to plants after they have cracked and roots are over an inch. Been putting them in rockwool with heating pad (and then under small flourescent light once above the rockwool) but have had more than I'd like turn out duds. Is there a better way to ensure the seedlings don't perish?

I do 1/4" root and jiffy seed starter mix.

I hate sayingbut miracle grow seed starter mixed with some extra perlite has worked perfectly for me.

The best way would be not to let the tap root get to be an inch long before planting it.

You only need to introduce water and warmth to begin the germination process. I soak seeds in a cup of water for 12 hrs then plant them in good soil. They sprout a few days after that. Some seeds are just not viable but if it sprouts and then dies, theres a good chance the grower is killing it. The usual causes are too much water, heat, light and fertilizer/nutrients. Basically too much owner involvement.

Are you growing hydroponically?