Seedling deficiency?

One of my seedlings has yellow marks on the leaves tips.. it's in top soil so idk how it could be nuts burn?

Yup you got some nut burn there, I only give kelp juice when they are that young. Then feed when they get more leaves and nodes. It will grow out, other than that you look good nice and sturdy.
Moondance

I agree, definitely burned. When the plant is that young they don't require any nutrients from the roots. All of the nutrients seedlings use are stored in the cotyletons, which are the small round leafs that first appear. By the time those leafs yellow the plant has developed a root system capable of feeding from the medium. That's when you start adding nutes.

I have the same problem on a seedling except mine has a cope of the lower points on the leaf brownis color.
I have not given nutes just water from tap left out over night then PhD at 5 to 6 I use a cheap gh drop kit haven't bought a good.ph tester

I used ffof for soil

Seedling and deficiency cant be used in the same sentence. A seedling theoretically can live on just its cotyledons for up to 3 weeks I believe.

You can tell when to give the first feeding just by watching the cotyletons. When they've began to whither and become chlorotic it's time to feed if no organic amendments have been added to soil.