Brown spots on leaves

So I have brown spots on one of my seedlings and I was wondering what it is because I haven’t fed it anything? My soil is ocean forest soil so I’m wondering what could cause it ? Only on one of them so I’m wondering???

Those seedlings don’t need any nutes that early on. Sometimes depending on the pheno seedlings can be a little finicky and have issues like that. For example I have a seedling that grew extremely slow and took a week longer than the others to show it’s leaves and when it did they were discolored and had spots on them as well. Make sure you are not under watering or overwatering and focus on the new growth. If the new growth is coming in green with no spots then you are on the right track. I grow with FFOF soil and never use any nutrients at all