Generally it starts with PH levels like RbtAsq said and a better picture like everyone says. Flushing with PH'd water may be a good idea at this point, it never hurts.

Which FF nutrients are you using and how much are you using? I wouldnt go much over 1/4 strength in Ocean Forest Soil, and I over fed the hell out of my plants in hydro. I dont grow much in soil so I could be full of crap.  

https://www.growweedeasy.com/cannabis-symptoms-pictures