How often do you water? I noticed my seedlings start curling like that when I over watered and the lower leaves turning a little yellow just like yours are. I fed her some NPK nutes, eased up on the watering and the problem was corrected after a couple feedings, it really only looks like lack of nitrogen to me but I could be wrong. I use FFOF soil and typically don't have to feed for a while because the soil is so rich with nutes but after about 2 months I start noticing deficiencies just like you have here so I just slowly start feeding and they stay healthy, I always foliar feed extremely diluted nutes every other time I water to give a little encouragement.