I suppose it is nutrient related buy why is one looking normal? I used the same lot of seed starting medium for all three. I'm enjoying the fact they are growing well and have not croaked because of damping off disease.
Do you have a lot of trouble with damping off?
If so have you ever tried watering with chamomile tea?
We(kids) did a science project here years ago and it really does work
The seedlings' leaves on the odd looking cotyledon plants appear to be normal and unvariegated. One plant seems to be less green color in its leaves than the normal cotyledon plant.