yellowing tips, brown spots, Ca deficiency?

[justaseed]

I would also ask how often you are watering? Over watering often looks like other problems and a 3 week old plant shouldn't have a nute deficiency sufficient enough to cause that much yellowing unless you are growing in some sort of soiless medium that had zero nutritional value to start with.

i guess you are right, i always use a soiless mix and perlite mixed at a 1:1 ratio so there is absolutely nothing in there and my seedlings are usually severely deficient at 3 weeks if i have not fed them yet.