My father did that last year, and they never recovered. The ones that self seeded started later but did much better and got fairly huge!

It'll be a while before you can put them into the ground, so I would write them off and start another set of seeds, no earlier than 4 weeks prior to planting out.

Thanks swb! :) It's interesting b/c the zinnias and alyssum that I started in the same tray/same window are compact and growing well!

I'll resow cosmos outside when it gets warm.

I had two cosmos in each of two pots, otherwise identical. I pinched one plant in each pot and the cosmos I pinched both died, slowly.