Autoflower seedling problem

My seedling is beginning to have a really bright yellow color in the middle with two green spots on both of it’s outer leaves just need some info on what to do if someing is wrong

How close is the light? What kind of light?
If the light is far enough away, it’s probably rapid growth.

I have a 600 watt mars hydro above all six of my girls it’s about 22 in above them the one I have a picture of is the only one doing it that’s why I can’t figure it out