I've had that happen quite often, it can happen on any seedling. I always spray the shell of that seed with water until it gets soft (which happens fast). After that, it's usually easily pulled off (gently holding the green seed leaf with tweezers). Even if you break the tip of the seed leaf (cotyledon) off the seedling will continue to grow just fine. Just go slow and easy and you'll be fine.

Thanks. I tried to do that on Sunday evening and am worried that I may have mangled them - one seedling is still greenish and the other disappeared somewhere into the soil. Mostly I couldn't figure out how to water/soften the shells very well. Crossing my fingers!