Does anyone know what’s going on here

Can anyone help me with issue with indoor cannabis ? Not sure if it’s phosphorus and potassium or what but it’s getting worse not better. I’m using fox farm mixed with perlite, giving them PH Perfect advanced Nutrients, all the other plants are beautiful but this one is sickly as hell … Do I need to keep trying to save her or chunk her ?
im including pictures I took just a few minutes ago.
thanks ahead of time you guys
 

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