I know vegetables better than flowers, and these don't look like any vege I recognize. Can you send the pics to the seed company and ask them to ID them? They seem to be happy little plants :)

Look like barberries, an invasive, tick laden shrub.

I don't believe they're Berberis. Wrong shape cotyledons and wrong texture. Also they don't produce a clump of seedlings. The berries contain a single seed if I recall correctly.

What was the source of the seed?

They could probably be a lot of different plants at this stage but there is some visual similarity to Hypericum, which like Heuchera does start with an H.

**** UPDATE

Thank you all for trying. I was really stumped! It finally occurred to me, though. These are seedlings of Talinum Limon - Jewels of Opar. And it makes sense now why I thought they were heuchera because the flower stem is similarly tall and airy. Note to self to do a better job of labeling my seed harvests, LOL! Though I probably didn't in this case because I don't know the plant name off-hand and had to look it up.

So mystery solved, and thanks again!

Plant info