is this Nute burn?

[lx574]

My two girls ( bubba kush and white widow) are still another 4 to 6 weeks away from harvest. Is this nute burn and should I flush?

 

[homegrown]

No, i would say root issues. I think your using air pots from what i can see, and looks to be coco with no perlite. Hard to say whats up without some more info on your grow set up. Soil,coco,nutes,pH in and out, watering schedule...

 

[dilvish]

more info on your set up and habits...hard to diagnose with just pics.