Hi, I am using 6500K T8 fluorescent linear light bulbs (2 of them) to grow seedlings indoors and I am noting the following problems, so if anyone can help me with any of these, I'd appreciate it:

The stems of some of the seedlings do not seem to be getting any thicker or longer (eg: purple palace seedling). Instead it just keeps on producing more and more leaves and those leaves are getting big and the whole plant is actually supported on the side of one of these leaves instead of standing tall on its own stem. What am I doing wrong?

When I transplanted my young Lewisia seedlings into a bigger container (3"), I noticed that their stem was pretty thick and they were producing big, green leaves but their roots were very very small, I'd say even smaller than one of the leaf! And the root hadn't spread out, it was just a single, straight root. Should I give it time or was there something wrong with my growing medium?

How much of the seedling stem (below the growing point, from where all of the leaves arise) should be above the soil level? Because one of my coreopsis seedling is almost completely at soil level -_- and all of the leaves arising from the growing point seem to be coming out of the soil -_- Should I replant it into the same container with some stem, from below the growing point, above the soil level? If so, how much of it should I leave above ground?