No reason you need to feed a seedling in soil anything , and no reason to feed veg nutes to an auto in soil at all. In the future to gage how well you're doing you absolutely need to get an EC/ppm meter to measure your input and run off , only then will you be able to tell where you're at . I see you're not measuring pH either , looks like pH fluctuations caused some burn. Now seems like the issue has receded but you want to measure incoming pH for sure . Ex meter and pH strips my friend, they are a must for the master grower ! Hope this helps ! 🚀