My first grow, I had the same problem. Grew four strains, one being White Widow. Got a few weeks into bloom, one day after I watered and nuted, most of the top leaves looked pretty much like yours. Like a claw but pointing upwards, with brown and burned spotting.
My advice is to flush the affected plant(s). There is a sticky covering flushing here.
Soil Runoff pH, Flushing to correct lockouts- Why and how to do it!
If the other ladies are happy with their food, then keep feeding them at the current rate. Then just dilute that food with pH'd water for the querky querkle.
You didn't say what kind of Fox Farm soil you were growing in. If it is the Ocean Forest (?) stuff, I hear it is very hot so beware.
Why did you change your pH to 6.0 this watering? You should be around 6.5 - 6.7. I don't think this is your main issue but it may be secondary to the overnuting.
Good luck.
