Slowly acclimate to higher light and it should fix itself. Even leggy plants will back bud under good light and correct etoliation, to some extent.

Thank you! And thanks for turning me on to the term 'etoliation', which I hadn't known before. Reading on Wikipedia I understand that it refers to the various things that plants do in response to a lack of light, so that stretching towards the light source and therefore becoming leggy is one of those processes of etoliation. I believe you're saying that slowly acclimating the plant to higher light will correct the etoliation that the plant had engaged in (and maybe not just the legginess but other things that the plant did to compensate for lack of light).

Last thing: what does it mean for a plant to "back bud"? Thanks much.

Back budding means it can grow more leaves and branches on the stretched empty portion of stem. Needs good light and depends a little bit on species.

So "budding" here doesn't necessarily refer to flower buds but is being used in a generic way as in leaf buds, branch buds, etc. It's called back-budding because the process generates leaf and branch buds on stem (below the growing tip) that had previously been leafless and branchless. Is that called the internodes?

I'd say that sounds about right. =)

Thanks, everyone. I think I'm getting a good understanding of this now. Aruzinsky, I did expose these two leggy seedlings to full light right away, and one is doing fine but the other seems to have died. Whether it's because I exposed it immediately to full light I couldn't say. I think there are other unusual things going on in this magic seed tray as well. For one, out of 24 seedlings I planted in this tray, only two have germinated (though we're at the very beginning of the "Days to Emerge" range indicated on the seed packet, and I'm guessing that's why.)

Here's a photo of the poor seedling that didn't make it.

Did I mention that this is Orlaya (White Lace)?

Thank you, everybody – this forum is incredibly helpful to me.

"' poor seedling that didn't make it'"

"plastic dome for humidity"

That's almost certainly damping off disease fostered by high humidity and condensation dripping onto the plant from the top of the plastic dome. Those plastic domes are typically a bad idea.

See https://en.wikipedia.org/wiki/Damping_off .

I got rid of the dead seedling and soil in that one cell and threw it into the trash. I know damping off can spread very quickly into large populations. Before taking further action, I'm going to wait until I see any other symptoms. Today there are two new seedlings and they seem to be doing fine, though certainly each in a different stage of growth which seems to be the name of the game here in this Orlaya tray.

Here's my favorite; I call him Rudolf Nurayev:

The youngest of the bunch, still not fully adjusted to the idea of being above ground.

One of the two originals, not at all shy about spreading his wings to their fullest extent:

Same seedling, a view from the side: