I wouldn't be as concerned about stretch as i would be squatting if fact most stretched seedlings are only like that for awhile then you would never even notice this can also be used to your benefit if your planning on LST'ing them at all. i can only say my methods and what i know BTW i doesn't make me right at all I'm just a fellow grower like you guys but i can say what works for me
![Wink ;) ;)](https://cdn.jsdelivr.net/joypixels/assets/8.0/png/unicode/64/1f609.png)
Remember your using 600watts your never ever going to get to much stretch the light is just to powerful at those hight's. id say lower the 600 about 2ft from the roof and go from there let her get used of it then start to lower but always keeping the spectrum zone just out of reach so she needs to grow into it or you will encourage squatting.