mom2goldens said:Hello and welcome
Are you watering your seedlings from the top or bottom? I only see spots on a few of the cotyledons, so just trying to figure out your growing situation.
mom2goldens said:My opinion would be that those baby seedlings are way too young to be outdoors. I don't set out my seedlings until they have several sets of true leaves (those above the initial cotyledons). Even then, they should be introduced gradually---just a few hours in a shady/protected area and gradually increasing exposure. Spinach can take some cooler temps, but these babies are still pretty young.
Did you start these plants under grow lights (they look pretty healthy all in all)? If so, just keep them indoors under some bright light until the weather improves. A few spots on the cotyledons (seed leaves) probably won't hurt. It's not unusual for many plants that the cotyledons turn yellow and fall off once the true leaves start to grow.
Also, if you can bottom water (can't tell what type of growing pots you have), it's better for the baby plants. Don't fertilize more than 1/4 strength once you have at least 2-3 sets of true leaves.
sallyg said:Yes, bottom water.
This is not related to how you should care for these but they do not look like spinach seedlings to me. Spinach seedlings start with two long skinny cotyledons, not these rounded lobed ones. These look like a brassica.