The usual causes of this - insufficient sun, over-watering, damp-off, and insufficient nutrients - aren't commonly a problem with sq ft so I am wondering if this is a new bed, just constructed or have you successfully grown in it before? If so then I suspect the issue is low nutrients. Try feeding them a quick fix of a good liquid fertilizer.

In the photo your mix looks awfully "woody" to me. is it that way throughout or is that just a surface mulch? If surface mulch only pull it back from direct contact with the plant stem and mound up some soil around them. If it is the same throughout the bed then you may need to add lots of nitrogen to off-set the wood's nitrogen binding.

Dave

Looks like a new bed, fresh wood framing. And new at gardening? Sq ft is a good way to get started for first time gardeners as many things can fit in a small space and the learning experience begins...

Yes, as dave pointed out the top layer looks like mulch. Sometimes mulching is best once plants are up and established. And give a bit of room around the stems. Your plants should recover fine. They sprouted too shallow. You may have planted under the soil but watering and rain can move them up to the surface soil line. Plant in moist soil then tamp it down, plant seed, cover with some soil, then tamp down with your hand or the back flat of a rake to secure them in place. Then lightly water in again.

You could put in a few new seeds a bit deeper just for insurance. I always plant 2 or three in the intended spot for that reason, then thin them later and keep the healthiest ones. If a critter gets a few all is not lost.