purple edges on leaves

i have a 3 week old seedling and some of the tiny leaves are green but the very edge of the leaves are purple. also some of the new tiny leaves coming out are also purplish color, is this a bad sign?

plants use alot of P during seedling stage so could use some. problem is finding nutes with good level of P and low N and K that would otherwise burn them. if u r using soil, try wood ashes but do measure your ph as these are acidic as hell.