I've used Grow Big..it works fine.
Just spray them right before the lights go out.

KNowm.
I wouldn't be suggesting this.
If i didn't just have huge healing success with foliar feeding.
You know I used to feel the same as you.
Remember my last grow you saw.
Those plants never got touched with water on there leaves.
Not once. lol

But I noticed if a plant was yellowing from being root bound or under fed.
It will greem up in a maytter of hours with foliar feeding.
Give it a shot next time you see some yellowing.