Trimming the dead and dying...when to say when

I've run into some nute burn that has left some of my larger fan leaves rather damaged. I've replenished the tank and reset the levels. All is well other than the damaged leaves look too far gone. I understand its good practice to cut dead or dying leaves, but when does a leaf enter the terminal zone? The leaves aren't dead yet, but 40-50% of the surface area is spotted or crusted. I think they need to go. What should I do?