I have tried to grow lupins from seed. Only about 3 germinated and only one has survived but this one is not thriving. I think my soil may have been too damp but I think I only started watering more vigorously because it was already struggling to establish itself!
Lupins are a full sun plant. This one looks to have received too much water and not enough light.
If the outside temperatures allow transition this to outside in the shade for at least a few days and then move to full sun and plant in the ground.
Or
move to a higher light location and reduce watering.
