If I may offer some experience.....
First learn to read your plants. From what I see, this is what they have told me..
The frilled edge of the seedling leaves are as such because your environment is not in tune for a seedling, it's too dry. That's their way of attempting to regulate the rate of transpiration in comparison to the roots systems ability to translocate water and nutrients. Increase the RH or mist them with water 2x's daily, until the root system gets larger.
This is the reason for the mild nutrient burn you are seeing. In an increased attempt to translocate hydration, the young seedling is also distributing nutrients, and these are accumulating in the leaf tissue, thus causing "burn" or necrosis. It will grow out of it, just as long as you don't overwater or feed it for some reason, just mist it periodically to assist in slowing down the loss (shedding) of water and to allow the roots to catch up.
ideally you want to aim for 75-78F day
70-75F night
70-80% RH seedlings
50-65% RH veg
30-40% RH flower