Seedlings sometimes rise with the shell still clamped over the cotyledons, and pulling it off dry tears the leaves underneath. A drop of water left on the casing for an hour softens it enough to lift away with tweezers. Notes on this and other first week problems are collected at https://queenfeminizedseeds.com in the germination troubleshooting. Planting a little deeper usually stops it happening in the first place.
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