First grow please help

im on week 4 of flower today and two days ago a number of leaves on one plant curled under overnight and the next morning became black and dead at the tip to the point they crunched when touched, the day after the whole leaf would be pretty much dead. what could this be. its not root rot, and im growing in foxfarm soil with foxfarm nutes

on the guide you just showed me, curling like a claw or talon and dark tips are symptoms of over watering and nitrogen toxicity. If the soil is dry since yesterday when you last saw the damaged leaves at good health you can easily rule out over watering.

can you post a few pics?