My four plants were two weeks old on friday, and already roots are creeping out of the holes in the bottom of the pots. I figure it's time to transplant. I'm going to put them in 6" terracata pots, and that's where they'll live out the rest of their existance.
My question is this: is it safe to plant them a couple of inches deeper in these new pots? The first week of their growth I used a 65w incandescent and they grew to be a little weak

. The second week I switched to circular floros, and the tops have grown to be quite strong

. When I transplant, would it hurt the plant to add a couple of inches of soil around the stem? The first leaves are about 4 inches from the soil now, so I have some space to work with.
I'm worried that this could lead to root rot (or stem rot, as it is now). Of course, I want what's best for my babies.
